Assign staic drive letter to removable hard disks

I am trying to create multiple backup up jobs with multiple removable hard
disks. One job I want to assign several drives as g: and on another job I
want to assign several drives as k:. Is it possible for the OS to recognize
the different drives with the correct drive letter with out having to change
them each time I insert one of the removable drives. I have already formated
and assign the appropriate drive letter to each drive but when I take one out
and put the other in they all go back to the default last drive letter e:. I
want to assign different drive letter so I know if a drive gets left in it
won't get overwritten by the job that follows it. These two jobs backup
seperate data. For clarification I want removalble drives 1, 2, 3 assigned
to g: and I want drives 4, 5, 6 assigned to k:. I am running Windows 2003
Small Business server and have an external SATA drive that I am using for the
hot swap backup drive with the 6 different drives.

Thanks for any information to help resolve this issue.