The problem you face is the complicated logic. you need to consider every situation you will take on . I don't know how to explain it. you need to digest it on your own which is the only way you can enhance your skill . The more you learned from others , The more power you will have. "Also what happens if my first observation is greater than 200?" That will render more code and more comlicated logic. But that is easy ,once you can understand what I code. Good Luck. Ksharp ... View more