Import contacts with name and last name separated

how can I import contacts with name and last name separated?
if i use displayname, is imported as a single field.

example:
...
Dim contactName As String
contactName = c.DisplayName
...
Result: contactName = "John Smith"

i need to have:
contactSurname = "Smith"
contactName = "John"

there is a way to do it?

thanks