Typically, the buy-sell agreement should be handled by a family lawyer in real life, but as far as it goes for the Family Lawyer software, I don't think it supports this feature. I've searched through its options and files and I didn't find anything available for your inquiry. Probably, the feature that you need is not in the application and the release date can be a cause to this lack of features, because Family Lawyer is a very old application that is now sold through Amazon only.
I recommend contacting your local lawyer firms to ask them about the program they're using for this operation. You will have more luck this way.