Microsoft Excel's undo / redo feature behaves unlike any other program I know. The undo stack seems to be global across all open files, so that undoing sometimes switches to another file and undoes something you didn't want to undo. And if an edit you want to undo was before an edit in another file, you have no choice but to undo the other file.

I am not the first to complain about this - see "Excel's undo madness", about halfway down.

Besides "edit only one file at a time", is there a way to make Excel's Undo apply to the current file only?

I'm using Excel 2003 if it makes a difference. //

A: Open Excel itself in a new instance

For Excel's main shortcut you could simply add a /x flag after the address in the shortcut's Target field:

"C:\Program Files\...\EXCEL.EXE" /x

It also works for pinned start menu shortcuts in Windows 10 (You need to access the shortcut file in Start Menu\Programs directory)

Open Excel documents in a new instance

This solution works but makes the documents' icon changed which some may find it unpleasant.

To run .xls, .xlsx, .xlsm, etc documents directly in a new instance, you could first create a .bat file with the following content:

@ECHO off
start "" "C:\Program Files...\EXCEL.EXE" /x %1

Then you could simply associate each file format to your .bat file with Always use... checked. [Use a shortcut .lnk to the .bat file and associate the files with the .lnk with correct icon.]

Keep the ability to open files in the current instance
It's still necessary to open files in the current instance if you want to access the other files' content through formulas or VBA. In these cases, you could first open one file and then drag the other file(s) on the opened Excel window.

You could also use File > Open through the opened file. //

MS does this for Excel only due to cross-workbook references. The only way they can maintain integrity of formula relationships in that context is to maintain a single undo history. Further, to make it optional is extremely complicated: how does a user choose whether to have a single history or multiple histories? When would a user choose that? They could make it automatic basing on formula dependencies, but that can easily become impossible to manage logically and performance wise. Remember, they need to deliver a product that WORKS. –
Mr. TA Apr 19, 2016 at 15:47

@Mr.TA: Libre/Apache Office has links between files/sheets and they do undo on a per file/sheet level... just saying (that it is doable, totally doable, if you're not a lazy x -- which apparently seems to be the case with MS developers). –
Erk Feb 7, 2017 at 16:13

I can create cross-document links in Word, while also undoing in a single document. Clearly it can be done. Yes, the link may get broken, but that's my fault. I would greatly prefer that behaviour over this window-jumping undo-hell. –
JMD Jan 19, 2018 at 0:49