restrict a particular username to a class c segment

[Hement Gopal <hementg@xxxxxxxxxxxxxx>]

Hi all

I am running Squid 2.5 Stable 5 on Redhat 9 on  a class B network.

I want to restrict  a particular username to one of my class C segments 
using ACL's

Can anyone give me a pointer?

I would prefer to point the src and username acl to a text file using 
regex if it is at all possible.

Many thanks

Rgds,
Hement