Breaking the Billiard Ball

Your task is to determine what is the highest point from which you can drop a billiard ball without breaking it. You stay in front of a 100-story building and hold only two billiard balls to test them. If both of them break before you give the answer then you your task is failed.

What is the minimum number of throws you will have to make to give the proper answer?

Assume that if a ball doesn't fall apart you can reuse it.