Paul has already given you the tools and a tremendous amount of work. If this is important for you, take the time to learn it or hire some high school kid to put it together for you. That tutorial is the bible on doing date calculations and, yes, it does take some thought and some work.

Just play around with it and you'll be surprised at what you can do. This is a user-to-user support forum to give people assistance. It is structured on the idea of giving someone a fishing pole and teaching them to fish rather than catching the fish for them.