Unauthorised MFBF Transaction

[Swordsmen]

Hi, as the title i, got problem when someone form other department has always do the transaction
MFBF without my acknowledge and they also have the login id ( can do MFBF ) the problem is,
that login id originally was mine - have 2 login id 1-for Assembly 1-for Stamping, and 1 form stamping
was given to their department and their clerk to do the key-in process for transit part ( that part was not my duty to do, so in order they can do the mfbf for transit part, so they were given the id from stamping. now heres how the problem goes.. they should only do and only do MFBF on the Transit part only, but they also do backflush on the my part of backflush, so when summary report is release, there were lot of variance on the part, so how should i block the certain item that they cannot do backflush and just do their transit part only.