private static long GetNoMouseOrKeyboardOpTime()
        {
            PLASTINPUTINFO lastInputInfo = new PLASTINPUTINFO();

            lastInputInfo.cbSize = Marshal.SizeOf(lastInputInfo);
            if (!GetLastInputInfo(ref lastInputInfo))
            {
                return(0);
            }
            return(Environment.TickCount - lastInputInfo.dwTime);
        }
 static extern bool GetLastInputInfo(ref PLASTINPUTINFO plii);