Automating Mount and Eject of External Drive Partitions

I have two external firewire drives connected to my PowerBook which is
running OS X 10.4.3. One of these drives has two partitions and the other has
seven.

All of these partitions are normally the recipient of SuperDuper! backups and
other than when a backup is underway I would like to have them unmounted

The SuperDuper! backups are run automatically in the middle of the evening.
iCal events mount (if necessary) and eject the partitions so that the
appropriate ones are available when needed for a backup.

I have created an AppleScript that ejects all of partitions and have included
it in the LogIn Items list. The problem is that on sign-on the partitions are
mounted anyway. I've tried putting delays as the opening statement of the
script, but this seems to be inneffective.

After I have been signed on for a couple of minutes I can then initiate the
ejection script and it will work fine.

So, after all of the blabbering above, I would appreciate any suggestions as
to how I can automatically sign-on and have these partitions not mounted.

--
James L. Ryan -- TaliesinSoft