How i will use proxy in my lan computers

Hi

I have 15 systems in my lan. I want all systems use different proxies.

I do not want to install any proxy server or software in my main server. All compuers are connected to internet through my main server.

So is there any software or way available through which i can use proxies only in my lan computers.

hi friends, i found the solution through this website
http://technicalbliss.blogspot.com/2007/04/how-to-use-free-proxy-with-firefox.html

i get free proxies from a website
http://www.proxy4free.com/page1.html

I use foxy proxy to rotate ip address
http://foxyproxy.mozdev.org/downloads.html