What is your idea? A horse race would be held every hour. There would be, say, 6 horses, each with different odds. People could bet on the horse(s) they think will win.
Has your idea already been suggested in some form or another before? (Check the Suggestions forum for past threads with ideas the same or similar to yours.) A looooooong time ago
What does your idea entail? See first question
How can your idea be successfully implemented into the game as it stands? Simply add a page under the casino tag
What major changes would be needed to make your idea work? Make the feature in casino
What is the positive impact of your idea? Another gambling option!
What is the negative impact of your idea? Work for Squishy and more ways to lose money in the casino xD
How may your idea affect the rest of the userbase? They could bet on horses

Maybe add this to the new version of the game? While I don't frequent casinos, I do like this idea. A few casinos here are actually at the horse tracks so this would fit right in.

+1