If I understand this correctly, the short answer to your question is "no"
via the approach you outlined for a number of reasons (see alternative
option to accomplishing the same thing)

#1 - The FullName field is actually a "derived" field made up of the sum of
its parts (i.e. FirstName, LastName and all other name elements). The "Check
Name...." you're referring to simply displays a quick UI facility to enter
the individual components without going to the All fields tab otherwise
Outlook will try and determine what the individual pieces are suppose to be
based on the data entered in the FullName field. Similarly, if you import
data to the FullName field (via Outlook or any other way) - the individual
elements are filled by Outlook or alternatively, if you import the data to
the individual elements - Outlook derives the full name from those pieces.
No more - no less and you cannot over-ride this functionality (that I know
of).

#2 - Check Name.... is tied to those specific fields so not something you
could use as a pass thru to create another "full name"

#3 - Again if I understand this right, in order to do what you want, one
contact import record would contain the individual name values for for the
2nd and 3rd contact (i.e. FirstName2, LastName2, FirstName3,
LastName3.....and whatever other elements). Your objective is to create one
FullName field for each comprised of the appropriate individual parts. Not
possible the way you described (but certainly will stand corrected if
someone else knows this answer to be incorrect).

However..............some possible alternative approaches on the assumption
that you input data contains the individual name elements in separate fields
(i.e. FirstName2, MiddleName2, LastName2 etc etc).

#1 - Create the individual fields for your form and make these "Not Visible"
on your form. The create another combination or formula field that would
result in a "FullName2", "FullName3" etc making sure you take out
unnecessary spaces for any missing fields
#2 - Pre-process your input data file creating a "FullName2" field from the
inidividual pieces in the input data record and import the data accordingly.

If the above doesn't address what you're asking - then I'll have to leave it
to someone else who hopefully better understands the question better.

Irrespective of the approach, since you're using custom fields, you'll need
a 3rd party product to import data to custom fields.

Karl

___________________________________________________
Karl Timmermans - The Claxton Group
ContactGenie - Importer 1.3 / DataPorter 2.0 / Exporter
"Power contact importers/exporters for MS Outlook '2000/2007"
http://www.contactgenie.com