You have a challenege ahead of you, honestly.

Consider the following names:

Mike Brown => Easy.
John Paul Williams => Easy too.
Biff Mc Fly => This is harder.
Peter David Van Den Berghe => Now what do you have in mind?
Catherine Zeta-Jones => Got a rule for this one?

The point is, what constitutes a last name? In one of the examples above, Mc Fly is the last name. In another example, Van Den Berghe is the last name. ...You would never say, "Hello Mr. Berghe" ... It's Mr. Van Den Berghe, always. Yet how are you going to come up with a hard fast set of rules that take into account all possible forms of last names?

It's hard. You would almost need a known last-name lookup table to match against.