Unix and Win2K Share User Info

How do I get a new Win2K Server to trust user accounts already set up on a Sun UNIX server? Clients (NT, 98, Mac) currently have their user name and password validated by a UNIX server running Samba. I want to add a workgroup server that is primarlyaccessable to a small department for file serving. So, how do I have my Win2K server know user and password pairs when clients attach to shared folders on the Win2K server? I do not want the Win2K server to act as a domain controller for both servers…just the W2K server.