NPCs able to use "keys" for locked doors?

[madmedic446]

Is it possible to make a key, that can be given to certain NPCs, allowing only them to access doors that the keys work on?

Or...alternately...Is it possible to specify that only certain NPCs are allowed to enter an area?

 

I am trying to keep wandering settlers out from behind the counter of a diner...But I obviously want the NPC who is assigned to the cash register to be able to come and go freely.