Dave, I do not understand the problem quite well. Are you wanting to be able to split up the exercise in three drag&drop actions? Because that is not possible with the built in D&D wizard, it is considered as one 'interactivity' where you can opt for some preferences but not for a real split up. Maybe Pooja will not agree, or I don't get the problem. Personally in this case as I understand it, I would use the Interactive D&D widget from InfoSemantics: you can add 3 instances of that widget and have the control needed, which I'm afraid you'll not have with the wizard.
Lilybiri