This link must have been broken at some point. Looking for this article. Thanks!
I've developed a (paid-for) tool that will allow you to set up such "cascading" drop-downs very easily, based on a spreadsheet that contains all possible combinations. You can find it here: http://try67.blogspot.com/2014/11/acrobat-create-cascading-dropdowns.html
Here's an article on the topic:
And loads more info on a membership site: