can pf be used as a generic tcp proxy?

[-f <f_(_at_)_obiit_(_dot_)_org>]

hi there,

i am reading the pf docs on openbsd.org but i must confess i am
more and more confused...  if the topic is too lame, please
kind souls answer me off-list...

i am trying to accomplish the following:
a frined of mine has a ban for a certain site (w.x.y.z)
but can access any other site w/o problems.  what i would
like to do is set up a generic proxy on my firewall to let
him go to w.x.y.z thru my firewall (he is not on my lan):

my friend's browser -> openbsd-firewall:some port -> w.x.y.z:80
and back.

is this possible using only pf?  if not, what tools should i use?
i don't need caching, so squid is maybe an overkill?
-- 
i know nothing, but i know it fluently.