Hi,
You can use a script that uses
yourSubformName.access = "protected";
on each of your Subforms. This still lets users copy to their clipboard and paste in another application.
On the Subform that contains the unlocked field or button you'll need to
yourFieldName.access = "protected;
on each sibling field in that particular parent that contains the unlocked button/field..
I do this and have a field that has no borders or caption to indicate that it exists (invisible, so to speak). If a user (Administrator) knows where the field is they can enter the secret word and unlock the form with a script using .access = "open" on all the objects you locked. You can leave a button unlocked instead. You can also style a button so it can't be seen, too.
There are probably other ways to do it--but this works for me.
Good luck,
Stephen