Group Directories in Active Directory Se

I am trying to set up drives on my Active Directory Services. I figured out how to set a drive letter to a directory on the server and serve that to a user. Now I want to set up directories for my groups of users so that upon logon, I can server them another drive letter with a different directory. Examle:

I have Bob Smith – so he gets his “Bsmith on server (G:)”

now I want to create an “M:” for the Marketing department so when bsmith logs on, he will have both an M: and a G:. I also want to serve a “N:” to all the employees in my company. Does anyone know how to do this?