Easier way = Simply create a password for your accont (if you dont already have one), then just right click on the desktop, and choose properties, then click the screensaver tab. Now, pick any screensaver and set it to the time you would like to have it come on.. Now there is a checkbox that says "On resume password protect" (or something like that). Now you can leave it alone, and when the screensver comes on it cant be taken off until your password is typed in.... Problem solved...
Hope this helps, but I DO like Rex's idea too.... Consider it...
