Bandwidth using report for PPP User

Hi, We use our freeradius Server to authenticate PPP Users. I need a tool that give me a report about the consumed bandwidth of a user. Is there a tool that create such a report out of the freeradius logs? Is it also possible to create a alarm or start a action (Chaning a port Configuration), if a defined bandwidth is reached? In future we also like to use these information for billing. Thanks and best regards, Peer