Dial-up NS lookups

[root]

Hi,
I'm providing my users with dial-up access to Internet. I use
/sbin/request-route to initiate a ppp call to my ISP.
Now a new group of users (with their own telephone line and modem) ask
me for the same service.
I wish to use a single dial-up server to activate different modems basd
on the IP address of the requesting user.
Does anybody have some suggestion?

Thanks Thanks Thanks for any help

Dan