If I understand you right, you have a total of 600 points split among three resorts. You have enough points for
DCL if you use points from all three resorts, but you'd rather borrow next year's points from only two of the resorts, and use those resorts' points for your cruise, leaving your BCV points intact. (Presumably for a BCV stay you may be planning)
Yes you should be able to do this. Each of your purchases has a unique contract number with it's suffix ending, -001, -002, -003.
Just be sure the CM doing this knows which points you want to borrow from which contracts. Keep track of all your points for each resort and watch your banking windows for any points you may not be using.
Remember also, that any points you borrow from next year, cannot be returned to that use year so you will have to use them in your current use year.
Enjoy the cruise.