Oh, you just want an incrementing number field, not really
an AutoNumber field. In that case, I think that article is
unnecessarily complex. You don't need a query to find the
maximum value in the table, you can just use DMax instead
DLookup on a Totals query.
Instead of using the Current event, it's better to use the
form's BeforeInsert event to set the field's value:
Me.fieldname = DMax("fieldname", "table") + 1
The Insert events only fire on new records so you don't need
to check for Me.NewRecord