Dial up networking without an adaptor??

we have a customer who has WindowsNT RAS server with as ISDN adaptor.

we want to setup client PC’s in our office to log onto the customers domain and then be able to access other PC’s on the network with PCAnywhere

Trouble is, we do not haveISDN adaptors in each PC. If we did, we would configure dial up networking to use the adaptor.

instead, we have a router on our LAN which can be used to dial into the remote site (router is default gateway on each PC)

how can we configure dialup networking to use the router on the LAN as it is not a device directly attached to the PC?