Secrets of the Office Masters: Beware of Undo

Like all Office applications, Excel includes an Undo button and a corresponding keyboard shortcut—Ctrl+Z. Unlike Word, however, which stores an unlimited number of changes, Excel can undo only the 16 most recent actions. When the Undo buffer is full, the oldest entry in the list vanishes to make room for your most recent formatting change, move, copy, data entry, or other action. In previous Excel versions, a simple change in the Registry could expand the Undo buffer significantly; however, that Registry hack no longer works in Excel 2001.

Excel's Undo feature has other significant limitations. For example, if you delete rows from a list and then remove outlining, you cannot undo any changes. Likewise, adding a chart or other object to a sheet clears the Undo history completely. You have absolutely no warning before Excel clears the Undo buffer, and you cannot recover its contents afterwards.

If you're used to working with Word, where the Undo capability gives you a nearly limitless ability to "roll back" a document to a previous version, Excel's considerably less powerful Undo feature might result in a rude surprise. When making extensive changes to the structure or design of an important worksheet, we recommend saving interim versions of the worksheet as you work. This file-saving routine doesn't have to be complex; for instance, you might tack on a version extension—v1, v2, v3, and so on—at the end of the filename each time you save. This simple precaution can make it possible for you to experiment with a worksheet while still preserving the ability to retreat to an earlier version if necessary.