The customers arent sure just what the details of the Undo will be. They want to try it in action and refine it. The basic starting idea is that there will be an unlimited number of levels of Undo and that each character typed should be capable of being backed out, one at a time, by typing Ctrl+Z or selecting the Undo menu item. They arent certain about whether theyll want a bigger blob undone at a time, like a whole word, sentence, or paragraph. I figure that if we can undo each character typed and each menu action, that will be sufficient. Then, if they ask for word or sentence chunks , we can put that in. And my guess is that going one character at a time will be perfectly satisfactory.