Add a single record parameters table to your database. include a Yes/No field named UnLocked.
In your main form, add a subform bound to this table with a checkbox control for that field.
In the On Load event for each of your forms add the code:
Me.AllowEdits = DLookup("[Unlocked]","tblParameters")
Me.AllowAdditions = DLookup("[Unlocked]","tblParameters")
Me.AllowDeletes = DLookup("[Unlocked]","tblParameters")
When each form opens it will set those properties to the value of the Unlocked field. So if Unlocked is True, then those properties will be set to True, if its False then those properties would be set to False.