Hi All,
After spending at least 6 months on trying to figure out how i could redirect specific users and computers to multiple upstream proxy servers (And nearly getting there too) I came across this:
ISA Server (Forefront TMG) Toolkit - freeware utilities for Microsoft ISA Server (Forefront TMG)
I posted a new thread here a few months back in the Cisco CCSP area hoping that an ASA 5505 would solve the issue (Which it didnt by the way)
Anyway, a long story short... The Advanced routing and Proxy tool included in the FREE pack will solve my issue. If anybody here works at a School like i do, you will find this a hugely valuable tool as you can use ISA server for all users and configure it to redirect traffic for you, rather than configuring Proxy addresses for all machines (Which becomes a really arduous task when you must manually configure IP addresses on machines for it to work!!!)
Thought id share my pain with you all.