Although editing a worksheet is supposed to improve it, you might find that you've done something to a cell or range of cells that you had not intended. This is where the Undo feature comes in.
You can undo just about any action while working in Excel, including any changes you make to a cell's data. To undo a change, click the Undo button on the Standard toolbar (or select Edit, Undo ).
You can also undo an undo. Just click the Redo button on the Standard toolbar.
Undoing/Redoing More Than One Thing The Undo button undoes only the most recent action. To undo several previous actions, click the Undo button multiple times or click the drop-down arrow on the Undo button and select the number of actions you want undone.