private static extern bool _GetCursorPos(out POINT lpPoint);
 public static void UpdateLayeredWindow(
     IntPtr hwnd,
     SafeDC hdcDst,
     ref POINT pptDst,
     ref SIZE psize,
     SafeDC hdcSrc,
     ref POINT pptSrc,
     int crKey,
     ref BLENDFUNCTION pblend,
     ULW dwFlags)
 {
     if (!_UpdateLayeredWindow(hwnd, hdcDst, ref pptDst, ref psize, hdcSrc, ref pptSrc, crKey, ref pblend, dwFlags))
     {
         HRESULT.ThrowLastError();
     }
 }