Modifying the FilterAdvFind search query


I am trying to have a restriction on the end user search on Incident & Change module.

If the user is not filling in the date and hitting the search after filling the other parameters, I want to append the query with " and opent.time > '01/01/2013 00:00:00' " to the query.
Is this done through Doc Engine > Search Config ? . If yes, could someone guide me please.