Adding the exception

[#1]

I have the following case to solve:

Table 1 - Stock:

Cod, Quantity

01, 10

02,15

03, 10

Table 2 Sale:

Cod, Quantity

02, 5

03, 20

I made a graphical object (table dynamical) with Table 2, putting the Cod field as dimension and I used the expression for the sum of the quantity. But I would like to have a new expression with the quantity that was not sold.

Expected outcome:

Cod, Stock, Sale

01, 10, 0

02, 15, 5

03, 10, 20

I'm waiting for help

Ivo Rodrigues