I would try to compare some fares because there might be no price difference with an actual stopover. Nwa.com does not have enough flexibility... try calling. On a trip to Europe I wanted to stop in Boston and I compared the fares. In the end instead of a CVG-CDG segment I took a CVG-BOS-CDG with a 2 week stopover and it was just $2 more. I understand that this is a different situation, but I think it might be worth calling.