Using Linux and PPTP to provide VPN between offices

Hi all,

My company's headquarters provides a PPTP VPN for us field people working at
home to log into. Here at home I've got a router that allows a single VPN
connection, but that's it. I'd like to be able to connect my whole home
office to the VPN so that my network and the company network can be bridged.
It sounds like if my company used IPsec I could just buy a router, but they
don't.

I've got a linux workstation that will connect to the VPN for and I'd like
to share that connection with the other machines on my home network.
Unfortunately, I can't figure out how to set it up. Routing x.y.z.0 to my
linux box, which routes x.y.z.0 to the VPN ppp connection doesn't seem to
work.

I've got two ethernet cards in the linux workstation. I want the other
machines on the network to go through the router for all the traffic except
domain x.y.z.0 (my company), which should instead go through the linux box
that's acting as the VPN endpoint.

I've seen lots of diagrams on the web for bridging subdomains and doing IP
masquerading, but neither a subdomain nor IP masquerading seems like what I
need.

I'll be very grateful for any advice.

Paul DeWolf