share modem on NT server

It looks like you could set up a Demand Dial interface using RRAS for WinNT.
Not the normal RAS that comes with NT, the updated version, RRAS.
Here is a Technet article on thishttp://www.microsoft.com/technet/prodtechnol/winntas/proddocs/rras40/rrasch01.asp
(please remove any spaces)

And here is the URL to get RRAS for NT:
http://www.microsoft.com/ntserver/nts/downloads/winfeatures/rras/rrasdown.asp

hope this helps

After exhaustive searching and hours of frustration, I found very few third-party applications that allow modem-sharing from the NT Server. Intriguingly, Microsoft's own Small Business Server comes with a Modem-sharing client, but it is not available on its own.

Spartacom, however, is the one software developer that has been in the business for awhile and has a couple products for modem-sharing that would suit your needs. There are no less-expensive software alternatives to the Spartacom products, at the moment.

http://www.spartacom.com/

It really is unfortunate that there aren't many options available anymore. Perhaps some of the other products that might have been available have all been migrated to "Internet-sharing" programs.