@TomU: you mention the wizard. Hence I understand you're working on the promotion request workflow (and wizard).
This piece of code is more likely applicable for change management workflows that contain a real setup participant task.
In your case, there is unfortunately no way to check this upon the wizard completion (unless with some tricky customization). I would rather suggest to use the business rules, but here again, nothing exists OOTB (at least to my knowledge).