As suggested in post7, more of the code might be helpful. The whole thing might be avoided by dim'g as variants instead of strings. Alternatively, more control over data entry is warranted so that neither first or last name can be null or "".
Empty is only really useful for variants because when initialized, a variant behaves as if it were both 0 and a zero length string, and that is what Empty means. When validating controls, I always check for Null and "" by calling a public function.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.