Every Office programs allow to do undo to go to earlier step if you have done an error. If you done a mistake then how far back you can go is given below:

Outlook - unlimited undo’s
Word - unlimited undo’s
Access – 1 undo
Excel – 16 undo’s
PowerPoint - 150 undo’s
Publisher - 20 undo’s
FrontPage - 30 undo’s

You can modify the number of undos in Access and Excel by editing registry. We do not recocommend this however.

PowerPoint is set to 20 undos by default but you can modify it if you want. It is not suggested that you raise it too much as it cause problems in PowerPoint. Go to Tools, Options, Edit tab, and from there you can modify Maximum number of undos up to 150.