Usage Limit and Accounting Plan

Dear Team, I just done installation and configure FreeRadius for PPPoE users. And I need more feature to meet user requirement. Currently, it already work for bandwidth limit by use CISCO-AVpair attr to return to CISCO LNS. 1. I need to limit the user monthly usage, for example bandwidth 2Mbps with 5GB monthly usage. 2. After the monthly usage exceed, I want the user change their plan to 512Kbps for example. It would related to scripting, but I has no idea about scripting. If anyone already done with that, I really appreciate for your sharing. Thanks for helping from everyone in community. Regards, -- Sokphak