How to share modems for outbound calls

In a small office environment, I have 20 users (W98 & W2K) who need to dial out to service bureaus occasionally during the day. Rather than providing every PC with separate modems and phone lines, I want to install a few modems on the W2K server and share them with the users. The only information I can find on modem sharing is with regard to internet connection sharing. At another site, we used a Shiva LanRover to accomplish this, along with dial in lan access. This is over kill for this project. Anybody have any ideas how I can do this using a few in-expensive modems?