This is not tied to the MaintenanceFormToolstrip, it is tied to a business object. The maintenance form toolstrip just works through the integrity of the framework, so an Add just calls the Add() on the form, which in turn calls the Add() on a business object.
All you need to do is capture the EditingStateChanged event of a business object and place your code there.
As for you quote not working, I don't know. I will have to look into it later. Thanks.