function doclass3(do_val, wrid, pinv) {
    // do_val=1 // change writer
    var arr_val_do = new Array();
    var url = "";
    arr_val_do[12] = 'invoice';
    if(do_val==12) { url = "class/class.php?do="+do_val+"&wrid="+wrid+"&pinv="+pinv+""; }
    fenster=window.open(url,""+arr_val_do[do_val]+"","menubar=yes, copyhistory=no, location=no, toolbar=no, scrollbars=yes, resizable=yes, status=yes,width=850,height=500");
    fenster.focus();
}