Me.Undo just reverts the record back to when it was last not dirty, if you are doing any refreshes or anything along the way that will save the record. You should be fine to just make your button use vba and do FieldName=True or FieldName=False, as long as you don't refresh or do anything to save the record, the me.undo should still be able to take you back. That would apply to any changes to any fields that you make, as long as you don't initiate a save by leaving the record or coding a save or ctrl+S, then undo should be able to take you back.

To clarify, it is a Macro (Set Value) that is updating the control for the checkbox. I am not refreshing or leaving the record or saving. Escape and Undo will undo checkbox changes. Also the Undo Changes button does not activate unless I change something else on the form first. If I change checkbox before anything else, it does not activate.

I don't use macros so I can't say for 100% certainty, but set value may be an automatic saving when it happens.