short answer - no, much longer answer yes if you 'capture' the old value into a separate table, then allow a user to restore this value if they make an error - this last requires quite a bit of thought/scripting - how many iterations do you allow? how many fields can you recover? how do you 'finalise' a record before moving on, do you you allow users to go back and restore a value in an old record - what about if two (or more) users are using the same record - who gets precedence?
potential can of worms
The can of worms is made a bit simpler by the fact that I am the sole user.
I just want to be able to recover from an occasional "oops, I wish I didn't change that, what was the former value?" type error.
If you haven't exited the field, there's a keyboard shortcut to undo the edit.
If you haven't yet committed the record, there's a "Revert record" option that reverts the record. Note that simply clicking a blank area of your layout will commit the record.
Sometimes it's useful to set up a layout where data is added/changed in global fields and then you use scripts to move the data in and out of the global fields.
Hmm.... I wonder what the technical issue is preventing FMP from having a robust undo feature.
Oh well. Thanks.