How to map expression pedal to wah?

[thams]

On a Receptor VIP, how do I make an expression pedal (such as a Line 6 FBV) map to control a wah on a guitar patch (such as the Wow-wah! in the Revalver, for example)

Or if, instead, I was using a wah device as Mix Effect 1, how do I make the expression pedal drive the wah, rather than driving the dry/wet mix?