Increasing Undo Levels

As you are working with a worksheet, Excel allows you to "undo" previous actions and return your worksheet to the condition before that action was taken. Normally you use Ctrl+Z to undo an action or you can use the Undo tool on the toolbar.

By default, Excel maintains your last 16 actions (Excel versions prior to Excel 2007) or 100 actions (Excel 2007). These numbers of undo levels can be misleading, however. There are some actions that can clear out the undo stack, making it impossible to undo any previous actions. For instance, running some macro commands can cause the stack to be cleared, and (prior to Excel 2007) saving the workbook clears the undo stack. In addition, some actions cannot be undone (they don't get placed on the stack), but the list of such actions can vary based on the version of Excel you are using.

If you find that the Undo command is simply of no use to you, there are a number of possible reasons. One common reason is that you have AutoSave set up with a very short interval. Every time you save a workbook--whether explicitly or with AutoSave--the undo stack is cleared and you cannot undo anything that happened before the save. (This doesn't occur in Excel 2007 because Microsoft changed the program so that it maintains the stack through the save. You cannot undo the save itself, but you can undo actions that occurred before the save.)

Another possible reason is that the number of undo levels in your installation of Excel has been changed. This cannot be done within Excel itself, but can be done in the Windows Registry. If the Registry value was changed to some very low value, then the undo tool loses meaning. The following Knowledge Base article explains how you can make changes to the proper Registry setting in Excel 2000, 2002, and 2003:

http://support.microsoft.com/?kbid=211922

If you are using Excel 2007, you can make the change following the information in this article:

http://support.microsoft.com/?kbid=162944

While you can use these techniques to increase the number of undo levels as high as you want, Microsoft suggests you don't increase the undo levels above 100, as there may be a serious hit on the performance of Excel.