This is an un-moderated, volunteer-supported newsgroup devoted to questions
about MS Access table and database design.  It would help those of us who
might potentially respond if we knew a little more about what/why you want
to do.

Auto-filling a sequence of "numbers"/codes seems unnecessary in a relational
database.  It seems like something that would be done to create blank
records for a spreadsheet.  What is it that you are trying to accomplish by
doing this?