Bert:
If you are talking about the order of source files as displayed in the uVision2 IDE project window, it is easy to move the files in the list around. You just click and drag the file name up and down the list then drop it at the place you want it to be.

If you are referring to the link order of files processed by the linker then following text from the uVision2 help file should be useful to you...

The Project Window shows all groups and the related files. Files are built and linked in the same order as shown in this window. You can move file positions with Drag & Drop.

Hope this helps...
Michael Karas