function updateSearch() {
	var url = "/ajax_dupdate.php";
	var selbox = $('sortby');
	var selindex = selbox.selectedIndex;
	option = selbox.options[selindex]; 
	var sortby = "sortby=" + option.value;

	new Ajax.Request(url, {
		parameters: sortby,
		method: 'post',
		onSuccess: function(transport) {
			$('tablelist').update(transport.responseText);
  		}
	});

}