Then you have to code something like a vote function where every user (who is allowed to, e.g. who stakes coins or whatever) can submit the outcome of the event.
This vote needs to have a fixed timeframe and needs to be 'closed' before everyone has voted.
Still, this requires that at least 51%+ of the participants vote honest. You need to give an incentive for voting honestly (e.g. reward per vote or loss of collateral after wrong vote).