wanna record user_agent from specific client ip

Hi

 

I have a requirement

 

it seems impossible

 

 

we want to record user_agent from some specific client ip

 

 

when CLIENT_ACCEPTED {

 

if

 

{ [IP::addr [IP::client_addr] equals 174.76.19.40] }

 

 

{ log local0. " 174.76.19.40 uses [HTTP::header value user_agent]" }

 

}

 

 

this irule doesn't work,because HTTP::header can't be used in CLIENT_ACCEPTED event

 

How should I do to achieve this goal