my car key wont operate my central locking anymore! HELP?

My cenral locking via the key was working fine until stopped working all of a sudden. Put a new battery in key - no joy! Got it checked by mechanic - everything in car seems fine. The central locking works by the internal button and key is flashing as it should but nothing happens! Please help - desperately trying to keep my kids from letting themselves out of the car!

Any tips? I'v seen other posts about resetting the key for the immobiliser but not sure i should try it without confirmation it would reset for the locking mechanism.

Karen
May 2010