The Process Files step Include and Exclude fields are used to specify masks of files and/or folders to match on (they can contain filenames, but all entries are treated as masks to include or exclude by). The action processes any matching files in alphabetical order.
To specify a different order, prefix the filenames to be processed with a number (i.e., 000zFile, 001AnotherFile, 002Filex, etc.).
Alternatively, use the technique described in
http://www.kinook.com/Forum/showthread.php?threadid=231 to generate a list in the desired order, and use the Loop action to iterate over the ordered list.