How do i know the original clients IP address?

Hit a small snag with using mod_backhand.

In the pool of available servers, i have no idea what the client's IP 
address is.  When i look at the CGI information, the remote address is 
the IP address of the mod_backhand machine that proxied the request.

Is there anyway I can find this information out?  If not, where would 
one suggest I add this in the original source as a custom HTTP header to 
be passed on down to the server processing the request.

thx