the setQueryBuilderSource function pareses the criteria that are set by the addComparisonFromEdit and adds to the where clause if needed.
the following comparison:
$WADbSearch1->addComparisonFromEdit("registr_date","registr_date","AND",">=",2);
would add to the where clause if the registr_date form element from the search where filed in and look for an entered date in the data base greater than the one entered.
It would be added after the existing where clause