Implementing a "logout" sqlcounter

I am thinking of using sqlcounter to implement a "logout" counter, ie whenever I want to logout a particular user, I set something into the database, then the sqlcounter will pick it up, and drop the existing session. OK I read in some of the older posts, one way people have implemented this feature is via then spin off radclient. This has the disadvantage in that, if the radius client is behind somekind of firewall, the server initiated radclient will have problem sending this to the radius client. Whereas the radclient continually sending accounting info to the server, I thought doing the reject at accouting will also some what accomplishing the same purpose. Any comments ?