function HideModalPopup(popup) {

    var modalpopup = $find(popup);
    modalpopup.hide();
}
function ShowPopup(popup) {

   
    var modalpopup = $find(popup);
    modalpopup.show(); 

}
function onCalendarShown(sender, args) 
{
    var calendar = sender; 
    var screenTop = null;

      if (Sys.Browser.agent == Sys.Browser.InternetExplorer)
        screenTop = document.documentElement.scrollTop;
    else
         screenTop = document.body.scrollTop;

     var screenBottom = screenTop + document.documentElement.clientHeight;
    var diff = (getTop(calendar.get_element()) + calendar.get_element().offsetHeight + calendar._height) - screenBottom + 30

     if (diff > 0)
          calendar._popupDiv.style.top = (getTop(calendar.get_element()) - diff) + 'px';
  }

  function getTop(e) {
      var offset = e.offsetTop;
      if (e.offsetParent != null) offset += getTop(e.offsetParent);
      return offset;
  }