On demand Dialing?!?!

I have a stand alone win2000 server, with ISA server installed.I am using a dial-up to make other 5 PCs access the internet from the ISA server.Problem, How I can stop on demand dialing? cause the connection is not needed in a continous basis, only when needed.
One more thing, the browser on the server containing the ISA server is working,I know this problem, I solved it when using a two lan connections not a dial-up and a lan. so any clue..