Execute SQL command after Authentication

Hi Friends… i Would like to know, how to execute a SQL UPDATE command after my client Authenticate for example. After client Authenticate… i want to execute a UPDATE command to my database sending the NAS where the client is connected… i know that this information exist in radacct, but i need this information in another table… My RadAcct table has more than 9 millions of registers… and i don`t want to make SELECTs in this table. Tks for your Attention. Best Regards Marcelo Santoro