auto idle time logout and save open documents gracefully

I am using managed preferences in a lab environment with 10.5.4 and have set the machines to logout after 15 minutes of activity. The only problem is that people leave with a MS word or some other document open and the logout gets canceled by the dialog asking if they want to save changes. Does anyone know of a script or setting I can use that will just hit the default on all dialog boxes and/or force a logout? It's really bugging me. -c