script to automatically mount external usb hard disk

hi all,

I have a debian lenny 5.0 server without GNOME installed.
the server is at a customer's premise.

I want to backup data from the server to the external usb hard disk.

the backup will start at e.g 01:00 everyday.
the user will plug the drive before going home.
also the user will not be given any access to the server.

kindly help & advise me on a solution.
thanks

autofs/automount is one potential solution. udev is another possibility.