function loadListingAnnonce()  {
	Event.observe('select_order', 'change', updateOrder, false);
}

function updateOrder() {
	var item = $('select_order');
	var url = window.location.href + '&order='+ item[item.selectedIndex].value;
	window.location.href = url;
}

Event.observe(window, 'load', loadListingAnnonce, false);