Joint to Internet.

I have a domain runing Small Business Windows 2000 Server with subnet 255.255.255.0
It has a ISDN Router connect to internet.

I also have a PDC runing Windows NT 4 (IP:192.168.0.2 subnet mask 255.255.0.0)
This server provide service for 5 workstations. They all connected to this NT Server by 5 Dial up ISDN Router.

I want those 5 workstations have the Internet connection through the Router on my Windows 2000 domain above. Please help me with your sugestion for this scenario.

Note: I tried to connect a network cable between 2 HUP of 2 subnet: domain 2000 and domain NT4, assign the Gateway IP on NT4 Server point to the Router IP address on Windows 2000 domain but it does not work.