You could probably loop through the list of proper names (where is it, and in what form?) and set the field to a calculation using:
Substitute ( field ; searchString ; TextStyleAdd ( searchString ; italic ) )
where searchString
is the current value of the inner loop. The outer loop is, of course, looping through all found records. Hard to be more specific with so few details.
That said, IMHO it would take no more time and effort to fix the real problem here once and for all, i.e. separate the two facts into two individual fields.
Note also that there is an assumption here that the proper names match only themselves; for example, "Peter Pan, Peter Pan" would become "Peter Pan, Peter Pan" using the above method.