Help with undo

[kingofbigmac]

Is there a way to undo a certain change without undoing everything up to that point?

 

[kingofbigmac]

I forgot to mention that I'm using CS4.

 

[hawkeye]

Going back to a prior state can be done with the history palette, but you'll lose everything done after that point. Also on the history palette is a camera icon. Clicking it will take a snapshot of that state, and you can use that to go back to that point if necessary.
The best method is to use layers for just about all changes. At any time you can delete that layer and everything else will remain in tact.