OpenBSD pf

hello ,
I am a newbie in OpenBSD packet filter.
I wondered if anyone could assist me in writing a simple packet filter firewall on my OpenBSD v4.5.
All I intend doing is to have two firewalling machine on a separate network :
192.168.1.1
ext_if = xl0 (dhcp) // Internet interface
int_if=xl1 // Internatl interface

192.168.2.20
ext_if = rl0 = 192.168.1.120 (static IP) //
int_if=rl1 = 192.168.2.20


My problem is how I could have the first machine passing the webtraffic to the second firewall machine?
Please I wondered if anyone could send me a brief explanation on this. I am not running a webserver or services to the outside world.

thanks
Matt