Hi Matt! Unfortunately, your image is broken. You can try just copying and pasting it directly into here instead of hotlinking.
You're correct in that Measure Values (as a field) cannot be used in any calculations. You also can't specify multiple sets of Measure Values, so I don't think there's a good way around this, except maybe with data reshaping.
Thanks David, I actually got around this by pivoting the data - then I had a field I could include in calculations