Multiple Proxy Servers

Is is possible within squid to use a different proxy server based on an
IP address? I would like my users to have to enter a single proxy
server, and squid to take care of "farming" out the requests to other
(non-squid) proxy servers.

Would a proxy.pac file be the way to go here and are there any examples
of simple ones I could modify for this?

Thanks in advance...

--
Daron Barndon
Senior Network Engineer
Network Applications Center
Cable & Wireless Optus
Phn:    +61 02 9342 0864
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