According to a number of posts, I should be able (in Moodle 2.0.3) to create two questions that use the same dataset and then use the same values in the next question.
For example, "You have a square with a length of {l} and a width of {w}. What's the area?" I should be able to follow that up by asking for the perimeter using the same values. http://docs.moodle.org/en/Calculated_question_type#Synchronization
I am having a terrible time actually setting this up to work, though. I think I followed the directions in that the questions are in the same category and have the same number of datasets, but when I make a quiz with those two questions, I get different values for {l} and {w}.
It shows me that it recognizes the other dataset: