Controlling panning on the Reason mixer using a Nektar Impact

[Thousand Ways]

Does anyone have any idea how to do that? The Nektar Impact – which I've generally found the worst, most unintuitive waste of space I've ever spent money on – is supposed to have a "grab" function that allows you to assign knobs to parameters in Reason. But I can't get it to control panning of individual mixer channels. Is this possible?