SetCooperativeLevel in DirectDraw Flipping

Dear experts,

    I'm working on windows mobile 6.1.
I'm trying to create a very simple flipping demo. With flipping, setcooperativelevel ( ) needs to be in full screen execlusive mode.

I took the following steps:
1) Create a complex surface (with back buffer)
2) set cooperative level to full screen.
hr = pDD->SetCooperativeLevel(hWnd, DDSCL_FULLSCREEN );
3) memcpy my data to back buffer.
4) flip the surface.

It works fine, but i see a quick blink before i see the content of my back buffer surface
after flip.
I think the reason for that blink is because of step 2, on windows mobile,
when setting cooperative level to full screen, whole screen goes black.

How do i avoid this kind of blink, or how to I avoid the screen from going
black when setting cooperative level to full screen?

thanks!