Hide/Delete keepusaliveuser in radpostauth table

Dear all, I need to get a keepalive user for my NAS to be authenticated every minutes. Also, for monitoring purpose, I am using this table to check which user get authenticated. Is there a specific way to delete automatically or to say to the Radius server not to add this particular user in the database? In fact, I am authenticated this user every minutes so this table is not significant anymore. Thanks for your reply, Sylvain