The undo/redo feature works across sheets AND ACROSS DOCUMENTS. So basically if you are trying to keep a backup, but open both versions to adjust your work, your redo and undo will be actually happening across all sheets that you have touched, as well as in ALL SEPARATE FILES that you have opened.

And oh the undo/redo does not stack. If you break your undo/redo sequence (aka even writing a new letter), your previous undo sequence is totally ****ed.

For instance, if you undo your file 1 to some earlier work, copy and paste to file 2 for backup, you have broken the previous undo/redo sequence, and all of the work you've done in file 1 are now shit.

So yeah, half of my data are gone...... and I this issue being there since forever, why does anyone think this is a good idea? This is a STUPID idea, unless you provide a really good explanation to me and an example, or else, I'm saying it's stupid and that's the way I will tell people.

As I know, undo/redo this option works at Application level and will undo changes in the reverse order actions were made. The behavior of current version of Excel won't be changed.

The only workaround you can use is to select actions which you want to undo from dropdown list.

Please calm down, you need to take care about this action next time.

And this is a persistent problem, you can find users complained this issue in different forums. Even there is MVP made the suggestion to the product team about change this option in Excel 2013. But seems like nothing change.

:(