What do you mean if you move back to Developer's Mode? That doesn't make sense to me. Enabling code (or putting the database in a trusted location so you don't have to click the button each time) is simply just enabling or disabling certain actions deemed to be potentially dangerous by Microsoft. Things like being able to delete tables change values, etc.
If you are wanting to requery a subform from another subform's code it would be
Me.Parent.SubformControlB.Form.Requery