IIS to redirect sub-domain

Hi,

We currently have IIS set up on our Win 2003 server that is handling port 80
traffic via our firewall (for external access to Exchange). What I'd like to
do is create a new A NAME record (our domain is handled by GoDaddy/Plesk) for
a sub-domain of our domain (subdomain.domain.com) and forward it to the
public IP address of our network (which will hit the firewall). When you
browse to this new sub-domain, it will forward the port 80 traffic to the
firewall, which will in turn forward it to the Win 2003 server running IIS
(as above). What I'd like to happen is to configure (if possible) the IIS to
then forward traffic that specifically requests this new sub-domain to a new
server on our local network (so if you browsed to this particular sub-domain,
it would hit a different server on our local network than if you browsed to
the existing sub-domain we already have set up for access to Exchange - even
though both are forwarding to the same public IP address and both are using
port 80). Is this possible? If so, how do I do it on IIS? Any help is
appreciated. Thanks.

- marc