function createurl(form){
	var form;
	var url;
	if (form.buscar.value == ''){
	 	url = form.url.value+'/buscar/todas/'+form.combocat.selectedIndex+'/';
	}else{
		url = form.url.value+'/buscar/'+form.buscar.value+'/'+form.combocat.selectedIndex+'/';
	}
	return form.action=url;
}