smart iRule that sends a log/trap when 2 members of a 4 member pool are down?

@etc-haslb-1:Active] ~ b pool | grep panhangui   POOL panhangui-prd-pool LB METHOD round robin MIN/CUR ACTIVE MEMBERS 0/4   +-> POOL MEMBER panhangui-prd-pool/5.9.162.184:63433 active,up   ...