Add a Feedback layer to "Multiple Response" graded question?

Hello,

I am currently working on an eLearning with a few graded questions. The last is a Multiple Response question with four choices, and two of them need to be selected in order to be correct. My supervisor has asked if it would be possible for me to add a new "layer" (not "Correct" or "Incorrect") that would indicate that the user is "half-right" when either of these responses is selected without the other one. 

I have tried playing around with the Feedback Master to add a new Feedback layer with this verbiage, and though the layer has been created, I cannot get it to show when either correct response is selected without the other. I tried creating a trigger for this, but whenever I hit the "Submit" button, it still gives me only the "Incorrect" feedback layer. 

I have a feeling that this is tied to the fact that the Multiple Response graded question, by default (in Form View), only allows for two layers: "Correct" and "Incorrect." Is there a way for me to create a third Feedback layer while still using this type of Graded Question, or would it be possible via a Freeform Question? Please let me know your thoughts. Thank you!

- Christine R.