Chapter 27. Linking and Consolidating Worksheets

IN THIS CHAPTER

Various methods of linking workbooks

Consolidating multiple worksheets

In this chapter, I discuss two procedures that you might find helpful: linking and consolidation. Linking is the process of using references to cells in external workbooks to get data into your worksheet. Consolidation combines or summarizes information from two or more worksheets (which can be in multiple workbooks).

27.1. Linking Workbooks

As you may know, Excel allows you to create formulas that contain references to other workbook files. In such a case, the workbooks are linked in such a way that one depends upon the other. The workbook that contains the external reference formulas is the dependent workbook (because it contains formulas that depend upon another workbook). The workbook that contains the information used in the external reference formula is the source workbook (because it's the source of the information).

When you consider linking workbooks, you may ask yourself the following question: If Workbook A needs to access data in another workbook (Workbook B), why not just enter the data into Workbook A in the first place? In some cases, you can. But the real value of linking becomes apparent when the source workbook is being continually updated by another person or group. Creating a link in Workbook A to Workbook B means that in Workbook A, you always have access to the most recent information in Workbook B because Workbook A is updated whenever Workbook B changes.

Linking workbooks also can be helpful if you need to consolidate different files. For example, each regional sales manager may store data in a separate workbook. You can create a summary workbook that first uses link formulas to retrieve specific data from each manager's workbook and then calculates totals across all regions.

Linking also is useful as a way to break up a large workbook into smaller files. You can create smaller workbooks that are linked with a few key external references.

Linking has its downside, however. External reference formulas are somewhat fragile, and accidentally severing the links that you create is relatively easy. You can prevent this mistake if you understand how linking works. Later in the chapter, I discuss some problems that may arise as well as how to avoid them. (See "Avoiding Potential Problems with External Reference Formulas.")

27.2. Creating External Reference Formulas

You can create an external reference formula by using several different techniques:

• Type the cell references manually. These references may be lengthy because they include workbook and sheet names (and, possibly, even drive and path information). The advantage of manually typing the cell references is that the source workbook doesn't have to be open. The disadvantage is that it's very error prone. Mistyping a single character makes the formula return an error (or possibly return a wrong value from the file).

• Point to the cell references. If the source workbook is open, you can use the standard pointing techniques to create formulas that use external references.

• Paste the links. Copy your data to the Clipboard. Then, with the source workbook open, choose Home Clipboard Paste Paste Link (N). Excel pastes the copied data as external reference formulas.

• Choose Data Data Tools Consolidate. For more on this method, see the section "Consolidating worksheets by using the Consolidate command," later in this chapter.

27.2.1. Understanding link formula syntax

The general syntax for an external reference formula is as follows:

=[WorkbookName]SheetName!CellAddress

Precede the cell address with the workbook name (in brackets), followed by the worksheet name and an exclamation point. Here's an example of a formula that uses cell A1 in the Sheet1 worksheet of a workbook named Budget:

=[Budget.xlsx]Sheet1!A1

If the workbook name or the sheet name in the reference includes one or more spaces, you must enclose the text in single quotation marks. For example, here's a formula that refers to cell A1 on Sheet1 in a workbook named Annual Budget.xlsx:

='[Annual Budget.xlsx]Sheet1'!A1

When a formula links to a different workbook, you don't need to open the other workbook. However, if the workbook is closed and not in the current folder, you must add the complete path to the reference. For example

='C:DataExcelBudget[Annual Budget.xlsx]Sheet1'!A1

27.2.2. Creating a link formula by pointing

Entering external reference formulas manually is usually not the best approach because you can easily make an error. Instead, have Excel build the formula for you, as follows:

When you point to the cell or range, Excel automatically takes care of the details and creates a syntactically correct external reference. When using this method, the cell reference is always an absolute reference (such as $A$1). If you plan to copy the formula to create additional link formulas, you need to change the absolute reference to a relative reference by removing the dollar signs for the cell address.

As long as the source workbook remains open, the external reference doesn't include the path to the workbook. If you close the source workbook, however, the external reference formulas change to include the full path.

27.2.3. Pasting links

Pasting links provides another way to create external reference formulas. This method is applicable when you want to create formulas that simply reference other cells. Follow these steps:

27.3. Working with External Reference Formulas

This section discusses some key points that you need to know about when working with links. Understanding these details can help prevent some common errors.

27.3.1. Creating links to unsaved workbooks

Excel enables you to create link formulas to unsaved workbooks (and even to nonexistent workbooks). Assume that you have two workbooks open (Book1 and Book2), and you haven't saved either of them. If you create a link formula to Book1 in Book2 and then save Book2, Excel displays the confirmation dialog box shown in Figure 27.1.

Typically, you don't want to save a workbook that has links to an unsaved document. To avoid this prompt, save the source workbook first.

Figure 27.1. This confirmation message indicates that the workbook you're saving contains references to a workbook that you haven't yet saved.

You also can create links to documents that don't exist. You may want to do so if you'll be using a source workbook from a colleague, but the file hasn't yet arrived. When you enter an external reference formula that refers to a nonexistent workbook, Excel displays its Update Values dialog box, which resembles the Open dialog box. If you click Cancel, the formula retains the workbook name that you entered, but it returns a #REF! error.

When the source workbook becomes available, you can choose File Info Related Documents Edit Links to Files to update the link; see "Updating links," later in this chapter) After doing so, the error goes away, and the formula displays its proper value.

27.3.2. Opening a workbook with external reference formulas

When you open a workbook that contains links, Excel displays a dialog box (shown in Figure 27.2) that asks you what to do.

• Update: The links are updated with the current information in the source file(s).

• Don't Update: The links are not updated, and the workbook displays the previous values returned by the link formulas.

• Help: The Excel Help screen displays so you can read about links.

Security Warning for Links Excel 2010 features a new security feature. The first time you open a workbook that contains links to other files, you see a security warning below the Ribbon. The links will not be updated unless you click the Enable Content button. However, Excel remembers that you've deemed the workbook safe, so you won't see that Security Warning again. If you would like to disable these Security Warnings, use the External Content tab of the Trust Center dialog box and change the option for Security Settings for Workbook Links. To display this dialog box, choose File Options. Then click the Trust Center tab, and click the Trust Center Settings button.

What if you choose to update the links, but the source workbook is no longer available? If Excel can't locate a source workbook that's referred to in a link formula, it displays its Edit Links dialog box, shown in Figure 27.3. Click the Change Source button to specify a different workbook, or click the Break Link to destroy the link.

Figure 27.2. Excel displays this dialog box when you open a workbook that contains links to other files.

Figure 27.3. The Edit Links dialog box.

27.3.3. Changing the startup prompt

When you open a workbook that contains one or more external reference formulas, Excel, by default, displays the dialog box (shown in Figure 27.2) that asks how you want to handle the links. You can eliminate this prompt by changing a setting in the Startup Prompt dialog box (see Figure 27.4).

To display the Startup Prompt dialog box, choose File Info Related Documents Edit Links to Files, which displays the Edit Links dialog box (refer to Figure 27.3). There, click the Startup Prompt button and then select the option that describes how you want to handle the links.

Figure 27.4. Use the Startup Prompt dialog box to specify how Excel handles links when the workbook is opened.

27.3.4. Updating links

If you want to ensure that your link formulas have the latest values from their source workbooks, you can force an update. For example, say that you just discovered that someone made changes to the source workbook and saved the latest version to your network server. In such a case, you may want to update the links to display the current data.

To update linked formulas with their current value, open the Edit Links dialog box (choose File Info Related Documents Edit Links to Files), choose the appropriate source workbook in the list, and then click the Update Values button. Excel updates the link formulas with the latest version of the source workbook.

27.3.5. Changing the link source

In some cases, you may need to change the source workbook for your external references. For example, say you have a worksheet that has links to a file named Preliminary Budget, but you later receive a finalized version named Final Budget.

You can change the link source using the Edit Links dialog box (choose File Info Related Documents Edit Links to Files). Select the source workbook that you want to change and click the Change Source button. Excel displays its Change Source dialog box, from which you can select a new source file. After you select the file, all external reference formulas that referred to the old file are updated.

27.3.6. Severing links

If you have external references in a workbook and then decide that you no longer need the links, you can convert the external reference formulas to values, thereby severing the links. To do so, access the Edit Links dialog box (choose File Info Related Documents Edit Links to Files), select the linked file in the list, and then click Break Link.

Excel prompts you to verify your intentions because you can't undo this operation.

27.4. Avoiding Potential Problems with External Reference Formulas

Using external reference formulas can be quite useful, but the links may be unintentionally severed. As long as the source file hasn't been deleted, you can almost always re-establish lost links. If you open the workbook and Excel can't locate the file, you see a dialog box that enables you to specify the workbook and re-create the links. You also can change the source file by using the Change Source button in the Edit Links dialog box. The following sections discuss some pointers that you must remember when you use external reference formulas.

27.4.1. Renaming or moving a source workbook

If you rename the source document or move it to a different folder, Excel won't be able to update the links. You need to use the Edit Links dialog box and specify the new source document. See "Changing the link source," earlier in this chapter.

27.4.2. Using the Save As command

If both the source workbook and the dependent workbook are open, Excel doesn't display the full path to the source file in the external reference formulas. If you use the File Save As command to give the source workbook a new name, Excel modifies the external references to use the new workbook name. In some cases, this change may be what you want. But in other cases, it may not.

Here's an example of how using File Save As can cause a problem: You finished working on a source workbook and save the file. Then you decide to be safe and make a backup copy on a different drive, using File Save As. The formulas in the dependent workbook now refer to the backup copy, not the original source file. This is not what you want.

Bottom line? Be careful when you choose File Save As with a workbook that is the source of a link in another open workbook.

27.4.3. Modifying a source workbook

If you open a workbook that is a source workbook for another workbook, be extremely careful if the dependent workbook isn't open. For example, if you add a new row to the source workbook, the cells all move down one row. When you open the dependent workbook, it continues to use the old cell references — which is probably not what you want.

You can avoid this problem in the following ways:

• Always open the dependent workbook(s) when you modify the source workbook. If you do so, Excel adjusts the external references in the dependent workbook when you make changes to the source workbook.

• Use names rather than cell references in your link formula. This approach is the safest.

The following link formula refers to cell C21 on Sheet1 in the budget.xlsx workbook:

=[budget.xlsx]Sheet1!$C$21

If cell C21 is named Total, you can write the formula using that name:

=budget.xlsx!total

Using a name ensures that the link retrieves the correct value, even if you add or delete rows or columns from the source workbook.

27.4.4. Intermediary links

Excel doesn't place many limitations on the complexity of your network of external references. For example, Workbook A can contain external references that refer to Workbook B, which can contain an external reference that refers to Workbook C. In this case, a value in Workbook A can ultimately depend on a value in Workbook C. Workbook B is an intermediary link.

I don't recommend using intermediary links, but if you must use them, be aware that Excel doesn't update external reference formulas if the dependent workbook isn't open. In the preceding example, assume that Workbooks A and C are open. If you change a value in Workbook C, Workbook A won't reflect the change because you didn't open Workbook B (the intermediary link).

27.5. Consolidating Worksheets

The term consolidation, in the context of worksheets, refers to several operations that involve multiple worksheets or multiple workbook files. In some cases, consolidation involves creating link formulas. Here are two common examples of consolidation:

• The budget for each department in your company is stored in a single workbook, with a separate worksheet for each department. You need to consolidate the data and create a company-wide budget on a single sheet.

• Each department head submits a budget to you in a separate workbook file. Your job is to consolidate these files into a company-wide budget.

These types of tasks can be very difficult or quite easy. The task is easy if the information is laid out exactly the same in each worksheet. If the worksheets aren't laid out identically, they may be similar enough. In the second example, some budget files submitted to you may be missing categories that aren't used by a particular department. In this case, you can use a handy feature in Excel that matches data by using row and column titles. I discuss this feature in "Consolidating worksheets by using the Consolidate command," later in this chapter.

If the worksheets bear little or no resemblance to each other, your best bet may be to edit the sheets so that they correspond to one another. Better yet, return the files to the department heads and ask that they submit them using a standardized format.

You can use any of the following techniques to consolidate information from multiple workbooks:

• Use external reference formulas.

• Copy the data and choose Home Clipboard Paste Paste Link (N).

• Use the Consolidate dialog box, displayed by choosing Data Data Tools Consolidate.

27.5.1. Consolidating worksheets by using formulas

Consolidating with formulas simply involves creating formulas that use references to other worksheets or other workbooks. The primary advantages to using this method of consolidation are

• Dynamic updating: If the values in the source worksheets change, the formulas are updated automatically.

• Open versus closed: The source workbooks don't need to be open when you create the consolidation formulas.

If you're consolidating the worksheets in the same workbook and all the worksheets are laid out identically, the consolidation task is simple. You can just use standard formulas to create the consolidations. For example, to compute the total for cell A1 in worksheets named Sheet2 through Sheet10, enter the following formula:

=SUM(Sheet2:Sheet10!A1)

You can enter this formula manually or use the multisheet selection technique discussed in Chapter 4. You can then copy this formula to create summary formulas for other cells.

If the consolidation involves other workbooks, you can use external reference formulas to perform your consolidation. For example, if you want to add the values in cell A1 from Sheet1 in two workbooks (named Region1 and Region2), you can use the following formula:

=[Region1.xlsx]Sheet1!B2+[Region2.xlsx]Sheet1!B2

You can include any number of external references in this formula, up to the 8,000-character limit for a formula. However, if you use many external references, such a formula can be quite lengthy and confusing if you need to edit it.

If the worksheets that you're consolidating aren't laid out the same, you can still use formulas, but you need to ensure that each formula refers to the correct cell.

27.5.2. Consolidating worksheets by using Paste Special

Another method of consolidating information is to use the Paste Special dialog box. This technique takes advantage of the fact that the Paste Special dialog box can perform a mathematical operation when it pastes data from the Clipboard. For example, you can use the Add option to add the copied data to the selected range. Figure 27.5 shows the Paste Special dialog box.

This method is applicable only when all the worksheets that you're consolidating are open. The disadvantage is that the consolidation isn't dynamic. In other words, it doesn't generate formulas. So, if any data that was consolidated changes, the consolidation is no longer accurate.

Figure 27.5. Choosing the Add operation in the Paste Special dialog box.

Here's how to use this method:

Repeat these steps for each source range that you want to consolidate. Make sure that the consolidation location in Step 2 is the same for each paste operation.

This method is probably the worst way of consolidating data. It can be rather error prone, and the lack of formulas means that you have no way to verify the accuracy of the data.

27.5.3. Consolidating worksheets by using the Consolidate command

For the ultimate in data consolidation, use the Consolidate dialog box. This method is very flexible, and in some cases, it even works if the source worksheets aren't laid out identically. This technique can create consolidations that are static (no link formulas) or dynamic (with link formulas). The Data Consolidate feature supports the following methods of consolidation:

• By position: This method is accurate only if the worksheets are laid out identically.

• By category: Excel uses row and column labels to match data in the source worksheets. Use this option if the data is laid out differently in the source worksheets or if some source worksheets are missing rows or columns.

Figure 27.6 shows the Consolidate dialog box, which appears when you choose Data Data Tools Consolidate. Following is a description of the controls in this dialog box:

Figure 27.6. The Consolidate dialog box enables you to specify ranges to consolidate.

• Function drop-down list: Specify the type of consolidation. Sum is the most commonly used consolidation function, but you also can select from ten other options.

• Reference text box: Specify a range from a source file that you want to consolidate. You can enter the range reference manually or use any standard pointing technique (if the workbook is open). Named ranges are also acceptable. After you enter the range in this box, click Add to add it to the All References list. If you consolidate by position, don't include labels in the range. If you consolidate by category, do include labels in the range.

• All References list box: Contains the list of references that you have added with the Add button.

• Use Labels In check boxes: Use to instruct Excel to perform the consolidation by examining the labels in the top row, the left column, or both positions. Use these options when you consolidate by category.

• Create Links to Source Data check box: When you select this option, Excel adds summary formulas for each label and creates an outline. If you don't select this option, the consolidation doesn't use formulas, and an outline isn't created.

• Browse button: Click to display a dialog box that enables you to select a workbook to open. It inserts the filename in the Reference box, but you have to supply the range reference. You'll find that your job is much easier if all the workbooks to be consolidated are open.

• Add button: Click to add the reference in the Reference box to the All References list. Make sure that you click this button after you specify each range.

• Delete button: Click to delete the selected reference from the All References list.

27.5.4. A workbook consolidation example

The simple example in this section demonstrates the power of the Data Consolidate feature. Figure 27.7 shows three single-sheet workbooks that will be consolidated. These worksheets report product sales for three months. Notice, however, that they don't all report on the same products. In addition, the products aren't even listed in the same order. In other words, these worksheets aren't laid out identically. Creating consolidation formulas manually would be a very tedious task.

Figure 27.7. Three worksheets to be consolidated.

To consolidate this information, start with a new workbook. You don't need to open the source workbooks, but consolidation is easier if they are open. Follow these steps to consolidate the workbooks:

Excel creates the consolidation, beginning at the active cell. Notice that Excel created an outline, which is collapsed to show only the subtotals for each product. If you expand the outline (by clicking the number 2 or the + symbols in the outline), you can see the details. Examine it further, and you discover that each detail cell is an external reference formula that uses the appropriate cell in the source file. Therefore, the consolidated results are updated automatically values are changed in any of the source workbooks.

Figure 27.8 shows the result of the consolidation, and Figure 27.9 shows the summary information (with the outline collapsed to hide the details).

Figure 27.8. The result of consolidating the information in three workbooks.

Figure 27.9. Collapsing the outline to show only the totals.

27.5.5. Refreshing a consolidation

When you choose the option to create formulas, the external references in the consolidation workbook are created only for data that exists at the time of the consolidation. Therefore, if new rows are added to any of the original workbooks, the consolidation must be re-done. Fortunately, the consolidation parameters are stored with the workbook, so it's a simple matter to re-run the consolidation if necessary. That's why specifying complete columns and including extra columns (in Step 3 in the preceding section) is a good idea.

Excel remembers the references that you entered in the Consolidate dialog box and saves them with the workbook. That way, if you want to refresh a consolidation, you won't have to re-enter the references. Just display the Consolidate dialog box, verify that the ranges are correct, and then click OK.

27.5.6. More about consolidation

Excel is very flexible regarding the sources that you can consolidate. You can consolidate data from the following:

• Open workbooks

• Closed workbooks. You need to enter the reference manually, but you can use the Browse button to get the filename part of the reference.

• The same workbook in which you're creating the consolidation

And, of course, you can mix and match any of the preceding choices in a single consolidation.

If you perform the consolidation by matching labels, be aware that the matches must be exact. For example, Jan doesn't match January. The matching is not case sensitive, however, so April does match APRIL. In addition, the labels can be in any order, and they don't need to be in the same order in all the source ranges.

If you don't select the Create Links to Source Data check box, Excel generates a static consolidation. (It doesn't create formulas.) Therefore, if the data on any of the source worksheets changes, the consolidation won't update automatically. To update the summary information, you need to choose Data Data Tools Consolidate again.

If you do select the Create Links to Source Data check box, Excel creates a standard worksheet outline that you can manipulate by using the techniques described in Chapter 26.