Hello All,
I don't have my 2002 book handy but 1999NEC 300-22 says no unless the wiring is needed for equipment inside the duct. The exception to 300-22 says "This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces" The way this was explained to me by my AHJ was that you cannot run wires in metal ducts but in homes with the above mentioned spaces used as ducts, wiring can be ran perpendicular to the length of the space.