How to get variance from two Comparision tables

table 1 having Scenario,Year and Period Slicers.

Table 2 having same slicers from same table,

Using edit interactions , stoped intercation with Table 1 and table 2 to compare both tables at a time.

So now my requirement is need to add 3rd table with difference of Table 1 , Table2 values.

If table 1 user select scenario as Actual,Year as 2023, Period as May

If table 2 user select scenario as Fcast ,Year as 2023, Period as May

Table 3 values should difference of Table 1 - Table 2 .

Ex: Selected values of table 1 Quantity - selected values of table 2 Quantity.

Can anyone help me how to derive a measure  based on selected values of same slicers. 

FYI - Backend having huge data unable to take duplicate table.