iptables: howto forward to different gateways

Hello,


I'm trying to route all trafic from a private (nat) network to an adsl
connection (214..),
the default gateway on my machine is 10.10.0.254 (of the corporate
network) because I need that for my normal desktop tasks
email/intranet/browsing.


Code:

NAT network My Machine
|192.168.0.10|-------|192.168.0.1|eth1:
|10.10.0.100|eth0:---corporate
mw/proxy---|gw:10.10.0.254|-->

|214.1.1.200|eth2:---adsl------------------|gw:214.1.1.81|-->


I'm using iptables to set this up and come up with this so far:

iptables -F
iptables -t nat -F

iptables -A FORWARD -i eth1 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth2 -j MASQUERADE

But this forwarding is not working since my default gateway (on My
Machine) is pointing to the corporate network.

I don't want to change the default gateway, all trafic from 'my
machine' has to go via the corporate network (something todo with my
developer tools I'm using and other machines wich trafic are routed via
my machine, all that traffic has to go through the firewall/proxy).

I only want traffic _from_ eth1 forwarded _to_ eth2 . No other traffic
is allowed to use the adsl connection.

How can I configure this, do I need an extra iptable rule or do I need
to alter my routing table (and if so how)?

Cheers,


Olivier