Undoing

[David Epstein]

Has anybody found a good way to make the standard "Undo" command apply to
specific scripted routines?

It seems pretty straightforward to store the "status quo ante" situation,
and catch an undo command that would put things back.  The problem is how to
make that option expire as soon as it should.  Certainly I'd want the
undo-this-routine option to disappear if the user has since done something
that Metacard itself makes undoable (like typing in a field); or if the user
has gone to some other card.  Is there a reasonable list of system messages
that might be intercepted and taken as signals to "clear the custom undo
buffer"?  Is there some way to detect when MC's own undo option (for its own
undoable routines) has become (or whether it remains) available?

Thanks for any thoughts.

David Epstein