I have used Exel for many years and never experienced this problem before.
One day I opened a file and it was okay; I could undo and redo with no
problem. I had emailed the spreadsheet to a friends computer, did some work,
saved it and sent it back to myself. When I opened it again the undo/redo
functions didn't work. When I first put the number in the cell before I hit
enter you can undo what you entered, but once you hit enter the icons turn
gray and don't work. I have researched every where I can think of, but still
cannot solve this problem. Your help will be greatly appreciated.