Changing 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 100 actions. This may seem like a lot of actions to track, but the quantity can be misleading. 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. In addition, some actions cannot be undone, as they don't get placed on the stack.

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:

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

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.