Understanding link formula syntax

Ideally, you won't have to enter too many external links manually. But it's good to know the structure of links in case you have to troubleshoot a problem. 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.xlsx:

=[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. Here's an example:

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

If the workbook is stored on the Internet, the formula will also include the URL. Here's an example:

='https://d.docs.live.net/86a6d7c1f41bd208/Documents/[Annual Budget .xlsx]Sheet1'!A1 

Creating a link formula by pointing

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

1. Open the source workbook.
2. Select the cell in the dependent workbook that will hold the formula.
3. Type an equal sign (=).
4. Activate the source workbook, select the source worksheet, and then select the cell or range and press Enter. The dependent workbook is reactivated.

When you point to the cell or range, Excel automatically takes care of the details and creates a syntactically correct external reference. When you're 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 (or URL) to the workbook. If you close the source workbook, however, the external reference formulas change to include the full path (or URL).

Externally linked cells can also be an argument to a function, like SUM or VLOOKUP. Anywhere you would point to a cell on the same workbook as the function, you can point to a cell in another workbook. A SUM function with an external link looks like this:

=SUM([source.xlsx]Sheet1!$B$3:$B$5) 

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 rather than use links as part of a larger formula. Follow these steps:

1. Open the source workbook.
2. Select the cell or range that you want to link, and then copy it to the Clipboard. Ctrl+C is the quickest way.
3. 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.
4. Choose Home ⇨ Clipboard ⇨ Paste ⇨ Paste Link (N).

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 a confirmation dialog box like the one shown in Figure 28.1.

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.

You can also 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 Data ⇨ Queries & Connections ⇨ Edit Links 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.

Opening a workbook with external reference formulas

When you open a workbook that contains links, Excel displays a dialog box (shown in Figure 28.2) that asks you what to do. Your options are as follows:

• 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 that you can read about links.

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 a dialog box with two choices:

• Continue    Open the workbook, but don't update the links.
• Edit Links    Display the Edit Links dialog box, shown in Figure 28.3. Click the Change Source button to specify a different workbook, or click the Break Link button to destroy the link and keep the current values.

You can also access the Edit Links dialog box by choosing Data ⇨ Queries & Connections ⇨ Edit Links. The Edit Links dialog box lists all source workbooks plus other types of links to other documents.

Changing the startup prompt

When you open a workbook that contains one or more external reference formulas, by default Excel displays the dialog box that asks how you want to handle the links (refer to Figure 28.2). You can eliminate this prompt by changing a setting in the Startup Prompt dialog box (see Figure 28.4).

To display the Startup Prompt dialog box, choose Data ⇨ Queries & Connections ⇨ Edit Links. The Edit Links dialog box (refer to Figure 28.3) appears. In the Edit Links dialog box, click the Startup Prompt button and then select the option that describes how you want to handle the links.

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 (Data ⇨ Queries & Connections ⇨ Edit Links), choose the appropriate source workbook in the list, and then click the Update Values button (refer to Figure 28.3). Excel updates the link formulas with the latest version of the source workbook.

Changing the link source

In some cases, you may need to change the source workbook for your external references. For example, say that 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 Data ⇨ Queries & Connections ⇨ Edit Links). Select the source workbook that you want to change, and click the Change Source button (refer to Figure 28.3). Excel displays the 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.

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 Data ⇨ Queries & Connections ⇨ Edit Links), select the linked file in the list, and then click Break Link (refer to Figure 28.3).

Renaming or moving a source workbook

If you or someone else renames the source document or moves 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.)

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.

Modifying a source workbook

If you open a workbook that is the source for a link, be extremely careful if the workbook that contains the link isn't open. For example, if you add a new row to the source workbook, all of the cells 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 by doing the following:

• Always opening 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.
• Using names rather than cell references in your link formula: This approach is the safest.
• Using a formula to refer to a cell: Your source workbook may not be structured to allow this method.

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.

By the way, notice that the filename isn't enclosed in brackets. That's because Total is assumed to be a workbook-level name and doesn't need to be qualified with a sheet name. If Total were a sheet-level name (defined on Sheet1), the formula would be as follows:

=[budget.xlsx]Sheet1!Total 

If your source workbook contains a list of months and values and you want to return the July value, you can use a formula such as the following:

=VLOOKUP("July",source.xlsx!MonthValues,2,FALSE) 

The source workbook has a workbook-level name MonthValues. If you used a normal cell reference, you would still have a problem if rows were inserted into the source workbook. However, by naming the entire range, you don't have to make a named range for each month separately.

Using 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.

We 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).

Consolidating worksheets by using formulas

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

• 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. 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 B2 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 in the same way, you can still use formulas, but you need to ensure that each formula refers to the correct cell—a task that is both tedious and error prone.

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 28.5 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 that refer to the original source data. So, if any data that was consolidated changes, the consolidation is no longer accurate.

Here's how to use this method:

1. Copy the data from the first source range.
2. Activate the dependent workbook and select a location for the consolidated data. A single cell is sufficient.
3. Choose Home ⇨ Clipboard ⇨ Paste ⇨ Paste Special. The Paste Special dialog box appears.
4. Choose the Values option and the Add operation and then click OK.

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.

Consolidating worksheets by using the Consolidate dialog box

For the ultimate in data consolidation, use the Consolidate dialog box. This method is 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 consolidation 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 28.6 shows the Consolidate dialog box, which appears when you choose Data ⇨ Data Tools ⇨ Consolidate.

The following is a description of the controls in this dialog box:

• Function drop-down list    Specify the type of consolidation. Sum is the most commonly used consolidation function, but you can also select from 10 other options.
• Reference 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    This contains the list of references that you've added with the Add button.
• Use Labels In check boxes    Use this 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.

Viewing a workbook consolidation example

The simple example in this section demonstrates the power of the data consolidation feature. Figure 28.7 shows three single-sheet workbooks that will be consolidated. These worksheets report three months of product sales. Notice, however, that all don't report on the same products. In addition, the products aren't listed in the same order. In other words, these worksheets aren't laid out identically. Creating consolidation formulas manually would be a tedious task.

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

1. Choose Data ⇨ Data Tools ⇨ Consolidate. The Consolidate dialog box appears.
2. Select the type of consolidation summary you want to use from the Function drop-down list. Use Sum for this example.
3. Enter the reference for the first worksheet to consolidate. If the workbook is open, you can point to the reference; if it isn't 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.
4. When the reference in the Reference box is correct, click Add to add it to the All References list.
5. 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.
6. 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.
7. Because the worksheets aren't laid out in the same way, select the Left Column and the Top Row check boxes to force Excel to match the data by using the labels.
8. Select the Create Links to Source Data check box to make Excel create an outline with external references.
9. 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 plus-sign 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 when values are changed in any of the source workbooks.

Figure 28.8 shows the result of the consolidation, and Figure 28.9 shows the detail information (with the outline expanded).

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 redone. Fortunately, the consolidation parameters are stored with the workbook, so it's a simple matter to rerun the consolidation if necessary. That's why specifying complete columns and including extra columns (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 reenter the references. Just display the Consolidate dialog box, verify that the ranges are correct, and then click OK.

Learning more about consolidation

Excel is 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 of 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.