Black backgrund painting if SetLayeredWindowAttributes is called.

Hi,

well I have a usual dialog based application with a resizable dialog.
Because I have some regions which gonna be transparent, I make in the
OnInitDialog the following call:

  const COLORREF crTransparent = RGB( 255, 0, 0 );
  LONG dwNewLong = GetWindowLong(m_hWnd, GWL_EXSTYLE) | WS_EX_LAYERED;
  SetWindowLong(m_hWnd, GWL_EXSTYLE, dwNewLong);
  SetLayeredWindowAttributes( crTransparent, 0, LWA_COLORKEY);

The MFC (or whoever) makes a not so funny black painting of the region which
will be bigger then the initial dialog. Without calling
'SetLayeredWindowAttributes' the black painting is not happend.

I tried to override the erase of background like this:

BOOL CBlaBlaTestDlg::OnEraseBkgnd(CDC* pDC)
{
      CRect rect;
      GetWindowRect(&rect); // Erase the area needed
      ScreenToClient(&rect);
      pDC->FillSolidRect(&rect, RGB(0,255,0));
      return TRUE;
}

but ... no chance, they are ... almighty. First apears the black painting,
then my green solid rect.
Has anyone, any idea how can I avoid this black painting ???
Thanks in advance!

Best regards,
Emil