Changing a Reservation

I just got an II conformation on a pretty good trade that I would like to piggyback on a week at one of my home resorts that I reserved some time ago. The problem is there is a two day gap between reservations. Can I change my reservation with MVC for a date that is two days later if that date is still available? If so, what will be the cost? I'm not a member of the DC. Also, what is the deadline for cancelling the II reservation?
Thanks and Happy Thanksgiving to all on this board!

DB

Changing a Reservation