Redirect IP to specific node or gateway

We have one set of IP's that due to the previous network that had them, we get blocked from a few sites. We have a backup ISP, and until we get a new block to eliminate this problem, Id like to be able to send traffic destined for the blocked sites out our backup network.

What I have so far is any any VIP that grabs all HTTP traffic going out and sends it to the router pool. I tried an irule like the following but no luck:

when HTTP_REQUEST { if {[HTTP::uri] contains "www.blockedurl.com" } { node backup_isp 80 } }

The VIP does have the HTTP profile assigned, and it is automapping to the default isp router pool. That pool then makes the decision which gateway to go out. What am I missing? Or how can I log it so I can see whats going on perhaps? Thanks in advance!!