I would like to butt in here.. I would just add one more suggestion on top of what EternalMyrtle has suggested.
Create an ACCDE file, which is the Compiled version of ACCDB, so they will not be able to look at the CODE, change any design of any objects. With ACCDR, the possibility is that if the user renames the file back to ACCDB, all functionality will be back again.
So Split the Database into Front End and Back End set up. Use the Front End ACCDB -> ACCDE -> ACCDR would be the best way to go around.