In this chapter, I discuss two procedures that are common in the world of spreadsheets: 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).
When you link worksheets, you connect them together in such a way that one depends on the other. The workbook that contains the link formulas (also known as external reference formulas) is called the dependent workbook. The workbook that contains the information used in the external reference formula is called the source workbook.
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 together 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”).
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.
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. 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.
The general syntax for an external reference formula is as follows:
=[WorkbookName]SheetName!CellAddress
Precede the cell address with the workbook name (in brackets), 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 refers to cells in a different workbook, you don’t need to open the other workbook. 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
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:
Open the source workbook.
Select the cell in the dependent workbook that will hold the formula.
Enter the formula. When you get to the part that requires the external reference, activate the source workbook and select the cell or range and press Enter. If you’re simply creating a link and not using the external reference as part of a formula, just enter an equal sign (=) and then select the cell and press Enter.
After you press Enter, you return to the dependent workbook, where you can finish the formula.
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.
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:
Open the source workbook.
Select the cell or range that you want to link and then copy it to the Clipboard.
Activate the dependent workbook and select the cell in which you want the link formula to appear. If you’re pasting a copied range, just select the upper-left cell.
Choose Home
Clipboard Paste Paste Link.
This section discusses what you need to know about working with links.
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 dialog box shown in Figure 27.1.
Normally, you don’t want to save a workbook that has links to an unsaved document. To avoid this prompt, simply save the source workbook first.
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 Office Prepare 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.
If you open a workbook that contains links, the links are updated to display the current values in the source workbook.
But what if 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 a dialog box, shown in Figure 27.2, that asks you what to do. If you click Continue, the file opens, even though the links aren’t valid (it displays the previous values for the links). If you click Edit Links, Excel displays its Edit Links dialog box, shown in Figure 27.3. You can use the Change Source button to specify a different workbook or click Break Link to destroy the link.
You can also access the Edit Links dialog box by choosing Office Prepare Edit Links To Files. The dialog box that appears lists all source workbooks, plus other types of links to other documents.
When you open a workbook that contains one or more external reference formulas, Excel, by default, retrieves the current values from the source workbooks and calculates the formulas. However, you can change this behavior by using the Startup Prompt dialog box (see Figure 27.4).
To display the Startup Prompt dialog box, choose Office Prepare Edit Links To Files, which displays the Edit Links dialog box. Then, in the Edit Links dialog box, click the Startup Prompt button. Select the option that describes how you want to handle the 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 Office Prepare 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.
Note
Excel always sets worksheet links to the Automatic Update option in the Edit Links dialog box, and you can’t change them to Manual, which means that Excel updates the links only when you open the workbook. Excel doesn’t automatically update links when the source file changes (unless the source workbook is open).
In some cases, you may need to change the source workbook for your external references. For example, you may 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. Select the source workbook that you want to change and click the Change Source button. Excel displays its Change Source dialog box, which enables you to select a new source file. After you select the file, all external reference formulas are updated.
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, select the linked file in the list, and click Break Link. Be sure to verify your intentions because you can’t undo this operation.
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 recreate 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.
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.
If both the source workbook and the destination workbook are open, Excel doesn’t display the full path in the external reference formulas. If you use the Office 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. Bottom line? Be careful when you choose Office Save As with a workbook that is the source of a link in another open workbook.
If you open a workbook that is a source workbook for another workbook, be extremely careful if the destination workbook isn’t opened. For example, if you add a new row to the source workbook, the cells all move down one row. When you open the destination 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 destination workbook(s) when you modify the source workbook. If you do so, Excel adjusts the external references in the destination 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.
Cross-Ref
See Chapter 5 for more information about creating names for cells and ranges.
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 these types of links, but if you must use them, be aware that Excel doesn’t update external reference formulas if the 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).
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 insist that they submit them using a standard format.
You can use any of the following techniques to consolidate information from multiple workbooks:
Use external reference formulas.
Copy the data and use Home
Clipboard Paste Paste Link.Use the Consolidate dialog box, displayed by choosing Data
Data Tools Consolidate.
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.
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 5. 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.
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.
Here’s how to use this method:
Copy the data from the first source range.
Activate the destination workbook and select a location for the consolidated data.
Display the Paste Special dialog box (choose Home
Clipboard Paste Paste Special). Choose the Values option and the Add operation, and then click OK.
Repeat these steps for each source range that you want to consolidate.
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.
For the ultimate in data consolidation, use Excel’s 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:
Function list box: Specify the type of consolidation.
Sumis 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). After you enter the range in this box, click the Add button 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: Displays 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: Adds 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: Deletes the selected reference from the All References list.
The simple example in this section demonstrates the power of Excel’s 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.
On the CD-ROM
These workbooks are available on the companion CD-ROM. The files are named region1.xlsx, region2.xlsx, and region3.xlsx.
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:
Choose Data
Data Tools Consolidate. Excel displays its Consolidate dialog box.Use the Function drop-down list to select the type of consolidation summary that you want to use. Use
Sumfor this example.Enter the reference for the first worksheet to consolidate. If the workbook is open, you can point to the reference. If it’s not open, click the Browse button to locate the file on disk. The reference must include a range. You can use a range that includes complete columns, such as A:K. This range is larger than the actual range to consolidate, but using this range ensures that the consolidation will still work if new rows and columns are added to the source file. When the reference in the Reference box is correct, click Add to add it to the All References list.
Enter the reference for the second worksheet. You can point to the range in the Region2 workbook, or you can simply edit the existing reference by changing Region1 to Region2 and then clicking Add. This reference is added to the All References list.
Enter the reference for the third worksheet. Again, you can edit the existing reference by changing Region2 to Region3 and then clicking Add. This final reference is added to the All References list.
Because the worksheets aren’t laid out the same, select the Left column and Top row check boxes to force Excel to match the data by using the labels.
Select the Create Links to Source Data check box to make Excel create an outline with external references.
Click OK to begin the consolidation.
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 destination range is updated automatically if any data is changed.
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).
Cross-Ref
For more information about Excel outlines, see Chapter 26.
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. Therefore, if you want to refresh a consolidation later, you don’t have to re-enter the references. Just display the Consolidate dialog box, verify that the ranges are correct, and click OK.
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 choose 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 doesn’t update automatically. To update the summary information, you need to select the destination range and repeat the Data Data Tools Consolidate command.
If you choose 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.