The only thing that you can do is use something like pgp, which is a key encryption tool. That way only the people with your key can get access to it. if you don't give it out, then no one can open it.
EFS won't do it as the local admins can gain access to the encrypted files since it's needed for the admins to do that. In a netowrked environment, you are at the whim of the IT department. I know cause that is where I work