aenhancers

Hey all
I've been working on a script that among other thing I wish that it would be able to lock the stretch attribute to its current value.
I managed to lock other properties like scale, position using an expression injector from my script , but because u cant set keyframes to the stretch attribute I could do the same there.
Upon understanding that difference I realized I need an event that would trigger an alert or something else that would then prevent the user from changing the stretch value.
i managed to change stretch value trough the script
currentLayer.stretch = 100.0
but not to lock it to the a value

Ideas anyone?
Thanks.