How to select specific vertices on a spline (so I can manipulate them) ?

I've got a very simple shape that I want to write an automated script for.

I want to select the two lowest vertices (they will both be on the same height on the z-axis, say maybe 0), and I want to invert that selection so I have all the other vertices and move those up the z-axis a particular amount.

How can I find my two lowest vertices in my spline?

PS - I am a newbie in MaxScripting and am going through AutoDesk's MaxScript Essentials book, but I can't see it in there.

Many thanks.