Help how to get a Total Substraction

Hello Community,

I hope you can suggest me how to get a "Total substraction" (dinamically)

I have a table where the progress is by Month like this

So I'm able to get use the visualization Array Table to show that info, so I need to show the difference between the lastDate and the oldDate dinamically, so the difference has to be calculated with the substraction of progress of selected months, examples:

if 2022 Qtr4 selected then difference will be December progress - October

if December 2022 and December 2021 selected then the difference will be of December 2022 - December 2021

I got to create the Measure to calculate it dinamically but I cannot add it properly to my array table 😞

I need to add the measure at the left as the default total column is shown when turned on, the measure column is desired to be shown like that

If I added it doesn't work, see below, I don't want the measure in Values and I don't want the Total column of progress but needed  turned on to show the measure column as desired

Any suggestion? How can I get it using array table or common table?

Measure: 

Thanks!!!