I think it would be much easier to modify the software on the users machines. You can add a timer that checks the time every .5 hours or so and if it is after 6:00 PM then shut down the software. Or a watch dog type addition to the software in that if the software is inactive for a given length of time it shuts down. Of course you need to consider any information that may need to be saved before it shuts down also. You could make a temp file on the...