It can't. use standard accounts. Or buy then flash drives. The entire point of an admin account is that a user can be trusted not to do things they shouldn't
The whole purpose of an admin account is that the admin account administrates the entire system.
On the other hand, if you want to soft restrict access you can remove the Administrators group from the permissions table and ensure that only each administrator has access by virtue of user account rather than Administrators group. However, they will be able to change the permissions themselves meaning that even if they do not own/have access to the file they can grant themselves the necessary permissions.