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bswank31 that's the problem, and I don't expect it will work with different selections in the slicer.

Here is the advice: There are always many ways to solve a problem, but the experts always suggest, following best practices and keeping your DAX simple by doing the heavy lifting on preparing the data and having a good model. Sometimes we go down this rabbit hole of solving a problem by writing a complex DAX which either doesn't perform or does not give the correct result. 

So the solution which I gave you is super simple because we have done the work on preparing the data to achieve the goal, it will perform on large data and it is super simple code. Now the choice is yours. Good luck!