Restricting logon access

I need to find a way of restricting access to a particular domain only. At present we have 2 domains here an nt4 based curriculum domain and a windows 2000 based admin domain. The workstations on the nt4 domain has been configured using system policys to allow access only to that domain, however I need to configure the windows 2000 workstations on the admin system to logon to that domain only. Any ideas?

Thanks in advance

Richard Shortland