You could use the gotfocus and lostfocus events of the subform to temporarily allow editing. Edits would be allowed everywhere, but only while focus is within the subform, hopefully within any field in the subform. The user would not be aware that editing is allowed in the main form, because as soon as they exit the subform for any part of the main form, you'd use the Me!allow=false to prevent editing again.
I didn't try this, but it might work.
Matt