Without seeing the exact data you are using, it's a little difficult to get specific, but I think that the answer is to go at the problem from another angle.
So if your parameter is subject and if you have multiple measures per subject, then you may need to have a calculated field for each measure that evaluates whether it is valid for the subject selected. Let's say you have two measures for Algebra (Alg_Score1 and Alg_Score2).
Create a calculated field called for Alg_Score1 with code like this:
IF [Subject] = "Math" THEN Alg_Score1 ELSE NULL END
Repeat that for each measure, then use those calculated fields in your view.
That's really just the first step, because then you're going to want to be able to hide the fields that aren't relevant. And that will require some data specific effort. And there may even be better or cleaner ways of doing this depending on your data set. If you can post a mock-up of the data (or even better, a packaged workbook), I (or others!) would be happy to take a look!
Was there ever a solution that worked for this particular use case that someone can share? I have the same issues that I am trying to resolve I have several measures that will roll-up to a parameter selected by my user. For example, I have a selection called Hotel in my parameter. When selected it will show Pref Hotel Booking, Non-Pref Hotel Booking, and Low Rate Hotel Booking. Each of those just listed are measures in my data.