I'm looking at booking a BTV-CVG-MSP-SEA run on DL/NW. The only reason I want to book that outbound is because it is cheapest. My question is, will I still be able to do an SDC three hours in advance to an all DL itinerary if one of the legs on my original itinerary (MSP-SEA) is on NW?

Merci et bon soir!