@andrew.gamble: The first thing to do is verify your AmiBroker license as described here: License Verified badge
Then you'll need to decide if you actually want to keep a stock in the rotation if it's dropped from the index. As that's a relatively infrequent event, I would think not, but it's really up to you. If I understand your question correctly, I'm not sure you're going to be able to model the behavior you want using AmiBroker's built-in rotational mode. We can discuss after you've been verified.