I see. That would require a little bit of hand coding. Try adding this after line 56.
if (isset($_GET['costoutdor']) && $_GET['costoutdor']) {
$WADbSearch1->addComparison("costoutdor","1","AND",">=",1);
}
if (isset($_GET['costindor']) && $_GET['costindor']) {
$WADbSearch1->addComparison("costindor","1","AND",">=",1);
}