frox+squid + iptables=confusion

[sham69]

Hi,
We have Squid running happily as our HTTP proxy, but can't get FTP through it, which is normal.
I have Frox installed, but am clueless as to how to get FTP requests to pass to Squid via iptables. The Webmin interface looks easier if I knew what to enter!
Squid proxy is using port 8080 and currently Frox is listening on port 2121.
How would I get client FTP requests to transparently get out?
I am obviously a newbie when it comes to port forwarding etc.
Thanks,
sham69

[sham69]

I guess what I don't understand is whether FTP requests go to Frox (port 21) and are redirected to Squid (port 8080) to be let out and if so what is the mechanism to redirect.
Do I use FORWARD, PREROUTING or perhaps another method altogether? Perhaps iptables is not what I should be using, as I don't need to use it as a firewall.
Do anyone actually use Frox? There is little info and most expects one to be an IP guru.
I search but get the same few HOW-TO's. My brain hurts.
Thanks........