How to prevent lan user transfer file to internet use MSN ?

[gjethro]

Hi,

Every one in my LAN behind wingate use MSN Messenger, Is there a way They can use MSN to chat BUT cannot transfer file out to wingate?

Now,They use socks come out,
I set the User: Bytes sent for client < a number
or User: Bytes received from client<a number
in socks policy, It does not work!!!

Is there a better Way?

Thanks!