Measure as Column with Changing Period Names

[TotunG]

Hi all,

I have a DAY slicer that has values like:

DAY 1, DAY 2, DAY 3, DAY 4

This is in a matrix that has these DAY values as columns so if I have selected DAY 1 and DAY 3 it looks like:

DAY 1	DAY 3
3	4
5	1
10	2
99	1

I also have a measure that compared the latest DAY value with the earliest DAY value so row 1 would return 1. 

However, I can't add this into the Matrix as a column to visualise this? 

What's the best way to do this so that users can still change the DAYs viewed in the matrix and the measure can be alongside it, dynamically calculating the differences?

Any help would be appreciated. I have initial thoughts that it may require changing how the data is structured.

[lbendlin]

Look into Field Parameters.