transparent marquee text above bitmap

Hello,

I want to draw a marquee text above a bitmap.

If the background of the text has a solid color:
-----------------------------------------------------------------
void COTextMarq::DrawItem( lpDraw..)
{
   HDC hdc = lpDraw->hDC;
   BITMAP hBit = ::CreateCompatibleBitmap(
        hdc, // handle to DC
        w, // width of bitmap, in pixels
        h); // height of bitmap, in pixels

   HDC hdcM = ::CreateCompatibleDC(hdc);
   ::SelectObject(hdcM, hBit);

   //fill background in hdcM
   //draw text in hdcM

   ::BitBlt(hdc, x, y, w, h, hdcM, 0, 0, SRCCOPY);
}
-----------------------------------------------------------------

To draw transparent,
I take clear bitmap and clear dc and draw the clear background
(I take it from an example):
-----------------------------------------------------------------
void COTextMarq::PaintBk(CDC* pDC)
{
    CClientDC clDC(GetParent());
    CRect rect;
    CRect rect1;

    GetClientRect(rect);

    GetWindowRect(rect1);
    GetParent()->ScreenToClient(rect1);

    if (IsWindowVisible())
    {
    if (m_dcBk.m_hDC == NULL)
    {
        m_dcBk.CreateCompatibleDC(&clDC);
        m_bmpBk.CreateCompatibleBitmap(&clDC, rect.Width(),
rect.Height());
        m_pbmpOldBk = m_dcBk.SelectObject(&m_bmpBk);
        m_dcBk.BitBlt(0, 0, rect.Width(), rect.Height(), &clDC,
rect1.left, rect1.top, SRCCOPY);
    } // if
    pDC->BitBlt(0, 0, rect.Width(), rect.Height(), &m_dcBk, 0, 0,
SRCCOPY);
    }
}
-----------------------------------------------------------------

I call PaintBk in the first part of the DrawItem() function.

But,
this is a little bit slowly and flicker a little bit.

So - I want to opitmize it:

- to draw into m_dcBk in DrawItem(),
then the background is not clear before the new Painting.

Is there a propper way ?

--
Thanks Frank Iversen