how to separate port line in multiwan?

[joehar]

hi all..
i need to configure the CentOS box as both proxy server and also router.
i set up the eth0 connect to ISP1,
eth1 connect to ISP2, and
eth2 connect to LAN
my desire is to direct port 80(http) and 443(https) through eth0, so that only two ports that can be entered through eth0.
and the other ports such as 39190, 40000, 16320...... etc through eth1.
actually, my point is want to seperate the line between browsing and game online.
is there the iptables rules should i add? and what is it?

sorry for bad english

thanks