forwarding internet traffice to pppoe dailup on Endian 2.2

[SuperBoss16v]

Hi

I Have endian Firewall 2.2 set up with a static public ip that is configures as Red interface (default gateway of machine), I have it configured for transparent http proxy, can i configure a pppoe dailup as a "secondry red interface" that i can forward only port 80 traffic through? should i do it in iptables or in squid? also when i add a pppoe dailup as another interface and activate it, t changes the default gateway to the pppoe.

sorry i know this is a mouth full.

Thanks

Bertie