Rewrite Proxy Question

I've been scrathching my head on this one for a couple of days, I'm not even sure it's possible as I'm fairly new to F5's and I am getting nowhere fast on this one.

 

 

I run hundreds of sites through a load balancer and at the moment, when we request one of our sites under http://www.site001.com/whitelabel - http://www.site150.com/whitelabel, we have an iRule that picks up the 'whitelabel' in the path and redirects the request to an alternative pool. The servers in this alternative pool run Helicon Isapi Rewrite which based on the URI, pulls a page in from http://whitelabelsite.com/landingpage/site001 - http://whitelabelsite.com/landingpage/site150. This page is then returned to the user under the original URI.

 

 

We are now making some amendments to our platform and I would like to do this on our Load Balancers if possible.

 

 

I can get this to work on sites already behind the Load Balancers using the ProxyPass iRule http://devcentral.f5.com/wiki/default.aspx/iRules/ProxyPass.html, but the difficulty I'm having is with the fact that the address I'm proxying is external to us.

 

 

Any ideas.

 

 

Thanks

 

 

Darren