Smith (2010a), Smith (2010b), Smith (2010c)

Most publishers actually specify the order to be based on  alpha (author) then year and then usually title, which may be what you are getting, and not in order of citation. That is because in the bibliography itself, that is how they want them to be listed. See http://community.thomsonreuters.com/t5/EndNote-General/Ambiguous-citations/m-p/29629#M6606 for a more detailed discussion.