How to log NAT info with explicit web proxy VS

Dear Expert ,

The LTM was configured as explicit web proxy and it is working well . There is one explicit web proxy VS with port 8080. I am trying to write the irule to log the IP info when the proxy traffic passing through the VS , such as client IP/port , NAT IP/port, destination IP/port. In normal load balancing case with pool , NAT IP/port can be logged by event " SERVER_CONNECTED" with "IP::local_addr" and "TCP::local_port" . However it can't used int explicit web proxy VS, maybe the pool isn't configured. Is there any ways to log the NAT IP and port ?