Redirect certain sites to external proxy using Squid

[Gaylord Van Brocklin <vanbrockling@xxxxxxxx>]

Currently, all desktops are setup via auto-detect/wpad to send http  
traffic to a pair of Squid boxes, which in turn send all traffic to  
another pair of AV proxy servers via round-robin cache_peer statements.

We have a requirement to access an external site that is only  
accessible via an external proxy.  Rather than changing the wpad file  
or desktop settings, and creating a firewall rule to allow those  
users directly out to the external proxy, is there a way to force  
squid to pass requests for a specific IP/subnet/hostname to a  
different proxy server?