How do I create a bitmap with an arbitrary color depth?

I need to be able to write a bitmap with an arbitrary color depth (probably 8- or 24-bit) to file, but before that, I want to write on it using GDI functions. The problem is, I only know how to make a bitmap that is suitable for drawing on, using CreateCompatibleBitmap, which gives me a bitmap with the color depth of the display. And CreateBitmapIndirect will give me a bitmap I can't draw on, if I give a color depth different from that of the display. I tried using calling GetDIBits and setting that header with a different color depth than what I had, but it didn't work as I wanted it to. Any help is greatly appreciated!

Donna