Thank you, gmaxey! As I wrote before my code works all right in the context of a macro. I have no problems with the reference numbers in the main document. All I need is a code that will ADD the letter 'a' after the reference number in the footnote area.
Perhaps someone will modify my code so as to obtain '1a ' instead of the wrong '1 a'. Here is again my wrong code:
With ftNote.Range


.InsertBefore supLetter 'i.e. the letter a
.Characters(1).Font.Superscript = True
End With