give each client a limited amount of internet usuage

Hi there is a clinet on my wlan that is downloading something 24/7. It cant be p2p becos the main proxy is not allowing that mac to use p2p. Can i maybe set a limit on that user? I want to stop him after he have used 3gig. Then only when i reset the counters then he should be able to surf the internet again. And can i give him 3gig each month and set the mikrotik to automatically reset the counters after teh last day of each month. And can i create a log of each client that shows me how much bandwidth he/she has used each month?

maybe something like this?
http://wiki.mikrotik.com/wiki/Automated_Usage_Script_without_usermanager

so all i have to do is go into winbox and to scripts and choose new script and paste the example? Oh yes and add my email address and email server settings? Then it should work?

it is a bit difficult. I was able to setup Logging Average CCQ and Wireless Clients Stats but not this one. Can you maybe help me. What must i paste in telnet?