Is there a way to make a pool failover into another pool or server

Here's the issue. I have a pool of web servers and a pool of app servers that are being load balanced by a BigIP. The customer would like when the number of connections to the web pool compared to the number of connections to the app pool reaches a ratio greater than 50:1 to bascially redirect the end user to a static web page saying that the site is too busy. Can this be done with an irule? Any help on how to do this would be greatly appreciated.