It depends upon how the full name field is formatted, i.e. FirstName
LastName, or LastName, FirstName, or LastName, FirstName Initial,
etc., and all records need to be in the same order.

For example, if all the records are like John Smith then you can use
the space to parse the field:
*** Back up your data first ***
Update YourTable Set YourTable.FirstName =
Left([FullName],InStr([FullName]," ")-1), YourTable.LastName] =
Mid([FullName],InStr([FullName]," ")+1);

The above will fail is some records are like John G. Smith, or like
John Herbert Smith, or like Smith, John or like Smith, John H. etc.

If the comma is the separator, just substitute InStr([FullName],",")
above, and reverse the FirstName and LastName field names.

Yes... but with some limitations. If you have a field FullName with
(say) "Tom Parker" in it, you can run an Update query updating
FirstName to

Left([FullName], InStr([FullName], " ") - 1)

and LastName to

Trim(Mid([FullName], InStr([FullName], " ")))

The limitations have to do with three word names. My friend Hattie Lou
Beckwith uses "Hattie Lou" as her first name; she'll go into the new
name fields as FirstName "Hattie" and LastName "Lou Beckwith" - both
wrong! On the other hand, a FullName like "Andeas de la Torre" would
be handled correctly; his last name is in fact "de la Torre". Do a
search afterward for

LastName LIKE "* *"

to find all lastnames containing blanks and fix them manually.

                 John W. Vinson[MVP]