Updating Persistence from an iRule

I'm trying to find a way to update my persistence from a URL parameter. Here is my problem:

 

 

Lets say I have a pool called test-pool. In that pool I have server1, server2, server3. I need to be able to test that an application is functioning properly on each of the server, but I cannot access the server directly. I have to go through the F5 BigIP. What I would like to be able to do is add a parameter like query string like f5persistence=server1 which then would tell the iRule to change the persistence to server1. Now, I have been able to use the 'node' command to forward requests to the correct server, but on the next click in the application the f5persistence parameter goes away and I get pushed back to the original server.

 

 

Any help would be greatly appreciated.