function doAjax(method,update,_params)
{
        var ajax_obj = new Ajax(wpath + 'ajax/?method=' + method, {'method': 'post', 'encoding':'utf-8', 'update': update, 'async':'false','autoCancel':'true'});
        ajax_obj.setHeader('<meta http-equiv="Content-Type" content="text/html; charset=utf-8">');
        ajax_obj.request(_params);
}
function update_fields(sender)
{
    params  = 'level1='+$('level1').options[$('level1').selectedIndex].value;
    params += '&level2='+$('level2').options[$('level2').selectedIndex].value;
    params += '&level3='+$('level3').options[$('level3').selectedIndex].value;
    doAjax('get_level4','level4_content',params);
}

function add_item(pid,id)
{
    params  = 'pid='+pid;
    params += '&id='+id;
    doAjax('add_item','item_content',params);
}

function del_item(pid,id)
{
    params  = 'pid='+pid;
    params += '&id='+id;
    doAjax('del_item','item_content',params);
}