>No, I´m trying to detect when a user pushes Undo or Redo option while edites a program with Modify Command.
Ah, I see. Perhaps you can do a custom version of the system menu - but then, I wouldn't know how to invoke the default behaviour if you replace the menu pad with your own.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)