You're going to need to do some work to make your logic a bit tighter:
What happens if a new record is entered, the combo set up, the user then
changes the combo to another name, and then creates another new record.
Does that get the 'next' one after what it was originally, or the one after
the one it was changed to?
What if a new record is added, then the user goes back to an old record
before entering a new record? 'Next' after which one?
What does 'next' mean? Alphabetical? What happens if a new name is
inserted?
Whatever logic you use, you're going to need a global variable that stores
the 'last' name. When you add a new record (which I think you're going to
need to do via a command button, rather than leaving the default navigation
buttons enabled) just use a function that finds that variable in the
recordset, moves to the next, and returns that name (or returns the 'first'
name if eof)
(...detail purposely missed out as pretty much impossible to put together
until you come up with answers to the first questions.)
Out of interest, why do you want to do this?