Need Shutdown Script for Backup

Hello all
I’d need a small script which should display a dialog box remembering the user when attemting to shut down the system whether he/she wants to wait for the backup and therefore postpone the shutdown or readily wants to shutdown the system. Additionally the script should then tell the system a what time to shutdown (e.g. 23:00 PM)
I’m not very familiar with AppleScript, but for an experiencend ‘Scripter’ this might be an easy task…
Any help is greatly appreciated.
Mark

"Additionally the script should then tell the system a what time to shutdown (e.g. 23:00 PM) "
Won’t the Energy Saver control panel schedule a shutdown time?
mg