function openCalendar (doc_base)
{
    cal_window = window.open (doc_base + "/cal.html", "cal",
        "menubar=no,resizable=yes,scrollbars=yes,width=360,height=350");
    cal_window.location.href = doc_base + '/cal.html';
    if (cal_window.opener == null) cal_window.opener = self;
}