is there anyway to forward outgoing packets to a local port?

i'm writing a http proxy software,
and i would like to forward all outgoing HTTP/HTTPS TCP/IP packets (e.g.
every packets go to destination with 80 port)
to a local proxy server port like "127.0.0.1:8080"

so that all http traffic can go via the proxy software without changing
client IE's proxy settings

is there any way or components to do that?

any ppl can give me idea to archieve the above?

thanks very much