If you want to back up to another PC on a network, an easy solution is to create a batch file with a copy command and then use Windows Task Scheduler to run the file late at night...
Another solution I've seen people use is to call a batch file at exit (using the shell command), zipping and copying the file to another drive. You could also -- rather than run a batch file -- export tables to another Access file at exit. And, I suppose, you could use the Timer Event to export your app's tables to another Access file.
A tape drive with backup software that can run on a schedule is yet another way to go -- no code needed.
Regards,
Tim