Make Sure Program Is Closed On All Machines Before Backup Runs?

I work in an architecture office using Quickbooks to track hours, expenses, billing, etc. The company QB files reside on the server in a shared directory that is mapped as drive Z: on all machines through a domain logon script that runs when each person logs on to their machine. The company file runs in multi-user mode so that everyone can access the file and enter their hours at the same time.The problem is that if anyone happens to leave Quickbooks open at night, the server backup process (running BackupExec) will skip the files that are in use, usually either 2 or 3 files. This is potentially bad news because if anything happened to the server the following day after those files were skipped, we would not have the file from the night before to restore, which could potentially mean lots of information lost (sometimes lots of info is entered in one day, especially on "billing" days).Sometimes people will leave in the afternoon for a meeting, thinking they'll be back later and leave their programs open. But then the meeting ends up running long and they don't come back until the next day. That's usually why Quickbooks ends up getting left open on a machine overnight.What I'm wondering is if there's a way to make the program automatically close, if it's open on any machine, perhaps just before the backup process starts on the server. Or, make the program close if the computer has been idle a certain amount of time.Is there any way to make this happen? All machines in our office that have Quickbooks on it run Windows 7, except for one machine that still runs XP.