@ful56_uk should have pointed you in the right direction; if not then give me a shout and I'll dig out some more sample code.
You can't do it with the "net group" command because it uses the API from Windows NT days (probably LAN Manager days!) which didn't support nested groups. You have to use the ADSI interface and then it will work well.
If you can't get that to work and you need it in a hurry then take the list of usernames and make a long list of:
Code:
net group <group with access> <username> /add /domain
(create them in Excel!)
followed by a matching list of:
Code:
net group <group with access> <username> /delete /domain
(remember that even if you don't have the username list that net group will give you that list)