How to create a "new vale" into a existing field

Question

Hi,

 

I have created a field called "PNL" using the CASE VALUE:

 

 

 

which has this values:

 

 

 

But now a want to add a calculated New Value on it to show in that query, this New Vale should be the result of COST+FINANCIAL INCOME;

 

NEW VALUE = COST+FINANCIAL INCOME

 

QUESTION:

 

How can add that new value into the PNL field?

 

any suggestion??

 

Thanks