transforming

Of course. What kind of transformation do you want?

What a coincidence. We both posted at the same time. My reply was for the first post, not the second.
Hmm, you want to change only particular values. No, there is no such matrix. But, maybe if you tell us about your case we might find some way out.

The correct way to use the ...UP functions is to not use them at all. Use vertex buffers. To change the values, use the transformation matrices. They are in all the SDK examples, including some of the simple tutorial examples. Or, you could use transformed vertices.

In any case, file access is going to be slow. Is there any way to read everything from the file before rendering and not read new data while you are actually rendering frames?