Query local active session database (radutmp)

hi :: Is it possible to query freeradius local session database (radutmp) to check for simultaneous use.? If exists delete it using radzap command and then only accept the Accouting Start packet which then eventually written to radutmp. I can write the script to delete but I have not ideas how to configure the radiusd.conf for my environment ( if it is can be done ). / Thanks BR