I've got a proggy that does the required work for me - reading & writing to the file, but how would I stop an epos user figuring out what it does & passing the correct parameters to fool around with things.

you need to pass it a password, but (& you would have to be really quick) ps aux would show the command line parameters passed.

I like the above idea - it's what I was trying to do with a shell script - Hmmmm.

Steve