function OpenWindowCentered(sURL,sWindowName,nWidth,nHeight)
{
    var nPosX = (screen.width - nWidth) / 2
    var nPosY = (screen.height - nHeight) / 2
    sWindowName = window.open(sURL,sWindowName,'menubar=no,status=yes,scrollbars=yes,width=' + nWidth + ',height=' + nHeight + ',top=' + nPosY + ',left=' + nPosX);
    sWindowName.focus();
}