I get it, yes you will need to this in a form.
I have designed systems such as this; you want the correct first name to
appear in mailings; however have the informal/friendly name for other
purposes.
What you need to do, probably on the AfterUpdate event on the FirstName
field on the form, is set the SalutationName (or NickName) field to the same
value.
Doing this on the AfterUpdate event is acheived using Me!SalutationName =
Me!FirstName in the event procedure.
If you already have data that you wish to update use the following SQL edit
to suit your table and field names,
UPDATE BusinessContacts SET BusinessContacts.SalutationName =
BusinessContacts.FirstName;