Need Help Using Slicer to Calculate Difference Between Two Dates

Hi Everyone -

I'm looking for help to use a slicer to dynamically calculate the difference between the two dates selected. This is for my "office market statistics project." Specifically, I'm looking to easily show the difference in absorption once a user chooses two dates.

Absorption is calculated by the difference in occupied square feet over a given period - it can be positive or negative. Occupied SF is calculated by subtracting the vacant SF from the "rentable building area (RBA)."

So for the situation below, the dates are 7/1/2014 - 4/1/2015, and in card visual below, it would display "3,486,142."

Occupied SF in 4/1/2015 = 136,426,764

Occupied SF in 7/1/2014 = 132,940,621

Absorption = 3,486,142

These numbers/stats will be updated each month and will all be in the same table. Any help would be greatly appreciated!

Thanks,

Paul