SQUID won't do bandwidth control, but you can use it to see what users have been downloading and to restrict what they can download. See http://www.ratsauce.co.uk/notablog/squid27setup.asp for my setup guide.
Remember you need to use a group policy to configure Internet Explorer to use SQUID as the proxy server.
To answer Ashian's question (this is a bit long to put in a comment):
local_network.txt contains your local network address. Open a command prompt and type ipconfig. You'll see something like:
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 192.168.16.128
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.16.254
If the subnet mask is 255.255.255.0 (it usually is) then the network address is the IP address with the last number set to zero. So in the example above it would be 192.168.16.0. In that case local_network.txt needs to contain the one line:
The default local_network.txt contains "192.168.255.0/24" as an example and you will almost certainly have to change it to match your network. Remember you need to restart the Squid service after making the change. If it still doesn't work post the ouput you get from ipconfig here.