irule to look into payload

I'm in need of an irule that looks into the payload of a packet for what website users are trying to hit. The vip services a proxy server which I don't have access to for viewing the logs. I need to know what they are trying to CONNECT to. Is there a way to parse that out in an iRule. Here is what i have so far and this works.

when HTTP_REQUEST { if {!([class match [IP::client_addr] equals user_group]) > [IP::remote_addr] } { log local0. } } }

This gives me the source of the traffic. The part I'm having problems with is the website they are trying to hit. Thanks in advance for your help