Shelf Adjustment Help!

Hello everyone!
I make a multibody model of a 2-shelf bookcase in Inventor. I rename each part of the bookcase. I make components to create an assembly with individual parts. From this multibody model, I linked the parameters together so I could change a size, and everything will update correctly in my assembly. Up to this point, everything works perfectly.
Now, my question is: currently this is a 2-shelf bookcase. How can I change the height of the bookcase to increase or decrease the number of shelves? For example, if the bookcase is 36" or lower then it will automatically change to one shelf. If it's 48" then two shelves. If 72" tall then 3 shelves.
Can someone show me how to do this please?

Thanks,
AN