D3D Keyframed Animation

I read in the DX8 SDK that you can do 3d animation via keyframes, which as best as I can gather are stored in the .x file. They seem to have no reference though as to how to do this, instead pointing you to a sample project. Looking at the sample project though, I couldn't figure out how to do it. Could someone explain in relatively simple terms how it is done/point me at a tutorial that explains it? That would be greatly appreciated. :)

i think i read something about keyframes in www.directx4vb.com...
check it out!

Thank you! :)