Firewall/NAT

I realize that multi wan is not supported, but would like to know if this is possible.  I currently have my isp connection on the wan port, which I use inbound traffic for one server.  I am moving to a new provider, so would like to move the wan port to my new isp, with new public ip address.  But I still need to keep the 2nd wan port active, to allow incomming traffic to the old public ip on old isp, until I can migrate off it.  I don't want to send traffic out the old isp, only the new.  So everything goes in and out the new wan, and still have wan2 (opt) avail to allow incomming connections to the server on the old address...  Is this possible?  I can put the old IP on the opt interface, and setup inbound nat I think, but not sure if it works without being able to put a gateway address in for the old ip?  Is the gateway needed?  If so, can I specify that somewhere?  Thanks

If the old ISP uses DHCP (ie cable modem) it could be possible to hack this in using manual NATing and firing up a DHCP client on the OPT interface you're using for that ISP. (using exec.php)
For PPPoE however it would be more complicated. You'd have to create another config file, fire up a virtual interface etcpp, make m0n0wall aware of it etcpp. I wouldn't even try then.

Thanks for the reply, that answered my question though, its not possible using built in options.  I don't want to hack anything, as that defeats the purpose of the unit as it is.  I will migrate this device over to pfsense for the purpose until I can migrate all the devices off the old service / ip.