[2008] Panning or scrolling an image with an indexed palette

I need to pan (or slide) an image up, down, left, or right. It's easy with the graphics object, but the problem is that the graphics object won't work with indexed images. I'm working with 4bppIndexed format. I can get it to work by converting the image to a non-indexed format, then use the DrawImageUnscaled method of the graphics object, then convert it back to an indexed format. The problem is that the conversion back to indexed format requires manually redrawing every pixel and that is way too slow for this app. It needs to be done in a split second.

Anyone know how to accomplish this much faster?

Wow, no answer? Well that makes me feel better in the sense that I was beginning to wonder how stupid I'd feel when I heard that the answer was super simple. Evidently there is no simple answer. I guess the next step is to hire a C++ programmer to make a custom tiny DLL to accomplish this. Any takers?