Field parameter set - if/then

Hi! I need help with a field parameter where I want a list of parameter options based on a filter selection. Here's some sloppy fictional data that simplifies my issue the best I can figure. 

We want to analyze class attendance statistics by different factors, like a student’s primary elective or what class they took. However, not everyone takes the same classes. Sytherins are the only ones who are schooled in being creepy, Gryffindors take sports history, but everyone takes Defense Against the Dark Arts.

I’m providing filter options and the column chart is using a parameter field for the legend. If you do not filter down to specific classes and use class as your legend, you’ll see all the data in the table, right?

But if I try to Hufflepuff attendance for a class in Creepin’, I get blanks, and correctly so, because Hufflepuffs ain’t creeps.

This year I have a new professor who has no clue that Hufflepuffs don’t creep and Ravenclaws don’t study sports history. They see this chart and immediately think the data is broken and they won’t use this report because it’s wrong.

So Dumbledore insists that this parameter be filtered, so you cannot select Creepin’ if you’ve selected Hufflepuff.

Using two filters that interact isn't an option because the purpose is to dynamically change the legend. 

But this report requires:

1. The legend MUST be dynamic
2. The chart can’t just be blank
3. Not accomplishing this with bookmarks because
   1. That’s what I’m currently using and it’s not flexible enough
   2. The user might eventually want to see a top 5ish students

What I need is a Nested IF Parameter that says,

If selectedvalue(house)=”Slytherin”, {S list of options},

If selectedvalue(house)=”Hufflepuff”, {H list of options}

If selectedvalue(house)=”Gryffindor”, {G list of options}

If selectedvalue(house)=”Ravenclaw”, {R list of options}

Thanks!