Create a Static Route
Example below is for World of Warcraft, use this if you have two nics on different networks.
route add 12.129.233.0 mask 255.255.255.0 192.168.1.1 -p
route add 206.16.235.0 mask 255.255.255.0 192.168.1.1 -p
route add 208.39.218.224 mask 255.255.255.240 192.168.1.1 -p
route add 12.129.232.0 mask 255.255.255.0 192.168.1.1 -p