In any login script you create, you could use the environment setting "Homedrive". This sets the drive letter.
You could say:
'homedrive=H:'
This would work in conjunction with the 'homeshare' variable, which would define the network path for your homedrive.
Your homeshare variable would look like 'homeshare=\\server1\sharename'
I know this is a pain, since this setting needs to be put in place within the user's own context, unlike the rest of your script. Anyone else know a better way?