Hello.
That can not really be done inside an Orchestration.
But, you would use Content Based Routing and Orchestrations with the Rules Engine to achieve something close to dynamic workflows. Each message would have properties set on it what would route it to the correct “next step” in the process. Then, at the end it will run through the rules engine again to see where to go next.
I saw a demo using this by a Microsoft guy. It was awesome.
Hope this helps.