//Open Back Office PopUp
function win_centrada(url, nom_ventana, width, height) {
    var str = "height=" + height + ",innerHeight=" + height;
    str += ",width=" + width + ",innerWidth=" + width;
    if (window.screen) {
        var ah = screen.availHeight - 30;
        var aw = screen.availWidth - 10;

        var xc = (aw - width) / 2;
        var yc = (ah - height) / 2;

        str += ",left=" + xc + ",screenX=" + xc;
        str += ",top=" + yc + ",screenY=" + yc;
        str += ",scrollbars=yes,status=yes";
    }
    window.open(url, 'ventana', str);
}