Scrollbar use is corrupting my bitmap - how to fix?

I have an app with a bitmap header embedded onto the main frame, and a property sheet below that. If I resize my app so scrollbars appear, and use the up/down buttons, my bitmap header will not get updated correctly. It becomes garbled/parts get erased, etc.


How can "scroll" the bitmap so it gets redrawn correctly?

Currently, I always display it 10 pixels below the top of the window. So when I scroll, this isn't what I want.


Thanks!


ps. I'm using some custom code to draw the bitmap - I'm not using a picture control.