Can you put it in as power walking?
Also, can you just calculate the caloric burn based on time and intensity on Spark? WW allows me to do that on their site for some of my gym class. So, when something doesn't exactly fit the category, I can still figure it out somewhat.
For a very, very general example - the average person will burn about 100 calories in 10 minutes of running at the highest intensity/speed they can safely manage. So I guess ratchet it down from there. Like, a good treadmill walk with an incline can burn a couple hundred calories in a half hour or so, provided you're going at a decent clip and decent resistance.