The only ways to force password based locking are by:1. using a program and...
The only ways to force password based locking are by:
1. using a program and filetype that support password locking
2. encrypting the file in an passphrase locked archive
If multiple users are signed into a singe account the system will not know the difference, you must use encryption to preserve privacy on the fle, but you must also remember that the file can still be deleted.