All the Office programs let you click on undo to go back to the previous step if you have made a mistake. These numbers may vary depending on your version of Office and might vary depending on the version. Here are the defaults.Outlook - unlimited undos
You can change the number of undos in Access and Excel by editing the registry. We don't recommend this though.
PowerPoint is set to 20 undos by default but you can change it if you like. It is not recommended that you increase it too much because it may cause problems in PowerPoint. FIle, Options, then Advanced and from there you can change the Maximum number of undos up to 150.