but my worry is what if they terminate excel or turn off the machine
accidently before my restore code can
run.

If they close Excel your Workbook_Close code should be called so settings
can be restored. In the unlikely event that they turn the machine off you
have nothing to worry about. Excel will only write the current settings to
the registry when its exit code runs, which it will not in this case.

--
Jim Rech
Excel MVP