Reply To: Can I add custom CSS for a post based on a Meta Box field state?

I think your solution is great. It might be a little bit tricky, but it works. While working with BB, I also did some tricks like that.

I'm thinking about another (similar) solution that might not need an textarea. I'd insert an HTML module with the CSS code, and use BB's Conditional Logic to hide it when the event is not repeatable. I think it's shorter than your solution.