Trigger iRule action when first packet hits ForwardingIP Virtual Server

Hello, We need to perform certain actions when the first packet (TCP SYN) hits forwarding virtual server which serves as a default gateway for some servers. Namely we need to do SNAT and select specific gateway/nexthop to route.

I've tried the following, but the problem is that the EVENT is not triggered when the first packet hits the VS - I believe it is triggered when TCP Handshake is done.

when CLIENT_ACCEPTED {
 log local0. "iRule even CLIENT_ACCEPTED triggered"
 if { [getfield [IP::client_addr] "%" 1] equals "192.168.20.0/24" } {
         
         SNAT 
        snat 192.168.10.234
         Set the next-hop to 192.168.10.201
        nexthop 192.168.10.201
   }
}

Is there a way to achieve the goal when the first packet hits Forwarding VS?