using different ports for vpn

Hi,

I have 2 Windows servers with rras as a vpn. There is an office where there
is 2 clients with only 1 external ip adresses. Client1 is on the LAN
interface and client2 is on the DMZ interface so they don't have access to
each other. I already redirect vpn ports on 1 server. I want to be able to
redirect vpn on another server. For that, I need to configure the vpn client
on xp to use other ports and of course configure the RRAS to listen for vpn
connexions on those ports.

How can I configure the xp vpn client and the rras to use different ports?

1- Is this possible?
2- Maybe the best way is to configure the xp client to use different ports
and translate those ports to the default ones in my firewall so I can NAT it
to the second server?

Basically, the result would be that when client1 does vpn, it is NATed on
server1 (LAN interface) and when client 2 does vpn it is NATed on server 2
(on DMZ interface) having only 1 external IP adress.

Thanks