Help me with calculcations

Im struggling with calculations. My db have 2 tables, one is revenue and the other is costs, both tables are linked by the Cost Center, I want to sum the results (Revenue - Cost) that the sum is higher than 0.
I dont know how to do this.
This way it will sum all, even if the result is less than 0.
Can someone help me?


If I understood well your question, in order to do that, you can use conditionals and set a different initial content when the result is less than 0

Ok, I got it, but if I do this, I will calculate each cost center each time. I want the bubble would like to create a SUM of all results >=0; but not seen all calculations, just the results. Is that possible?