try to communicate your Radius Client with Userman first..
then give each of your user a different username-password that u had added in Userman..that will do the work
Local and overseas traffic limiting example is given in the wiki, http://wiki.mikrotik.com/wiki/How_to_ap ... as_traffic
if you have any other questions about queues/mangle, you can ask it in the 'General Networking' section.