How to 'Forced Offline' on a pool member using irule.

Hello

With a big 11.6 ip We have an application where a servers are at 100% of cpu and memory with 300 sessions. Sessions have an average of 4 minutes. The connections are very intensive (fast and large numbers). The server can indicate a parameter in the http header where the number of session raise to 250 sessions. I would like to use an irule to put the pool member in "Forced offline" where that parameter come from th server. For exampe: HTTP_reponse . The advantage is the current connections will not be cut off. I can load balance to another server the traffic. There will be news connections sent up when the number of session goes under 250. Is there an irule to use "Forced offline" on a pool member?

Thx