Sarge
How about considering total kms travelled for all hits? A person with, for example, 10 bills having been hit from Saskatoon to Regina would have about 2700 kms 'earned', but a person with a bill going from Vancouver to Halifax will have earned more than that on a single bill. A bill getting multiple hits would earn all the mileage for the original stamper, but others would earn mileage only for the legs after they entered the bill.
DR, would an addition line like that be too hard to program?