[Storm]

What is your foundation for your heelwork? If the dog is sniffing the motivational aspect is lacking. Motivation in hand with association and anticipation is what builds focus and intensity in heel work. If you correct there must be a correct behavior in place in order for the dog to "release" by reverting to the correct learnt behavior, considering it is existent, other wise you will be just causing conflict and confusion. Behaviors can't be forced through correction, well maybe in a round about unfavourable way, but rather concentrate on the development here which may require you going right back to square one.