delta result from date based data drops via matrix table

Hi,

I have a fairly complex data system in which I need to report 3D design data (count, length, area and volume) on a weekly basis.

I want to get the delta of change. The images show what I'm working with.  I want to get delta of change for the values via the two most current dates 12/02/20 & 21/02/20. The other option is to have the data selected via a drop down box for "previous" and "current" with the delta. My key point is that I need to get the delta of the data drops.