MEASURE in the current row context

Hi everyone,

I need to create a visualization with a table that shows the substraction between 2 fields, both are coming from different tables of my model and the link between them is a "key" field.

Currently, the substraction is calculated in a third auxiliar table using the "key" field I mentioned before, and then just adding the result to the visualization.

I am wondering if there is a more smart way to do the same and I have worked in creating a MEASURE that could make the calculation in the context of the row, unfortunatly what I always get is the difference between totals.

To put it more graphical, I want YELLOW-RED in my last column:

 Image may be NSFW.
Clik here to view.

If you need some extra info do not hesitate to ask me.

Thanks a lot in advandce for your help.

Regards!