Measure traffic on ssh tunnel?

Hello,

I have installed the latest copSSHd to setup a ssh tunnel on windows 2k3. I would like to measure the monthly traffic that goes through the tunnel though (or total traffic until tunnel is closed) and am wondering how to achieve this. Is there any such functionality in openssh? Any suggestions how I should go about? 

More info: The tunnel will be from one local port to a port on a remote host. From what I understand the tunnel I want to measure will be something like: ssh -l username -L localport:remoteserver:remoteport localhost cat - 

Regards,
AFW