How to add a calculated row in the matrix ?

[Emeric59138]

Hi all, I am new in Power BI and I would like your help for a specific ask. 
I am doing a P&L in Power BI. 

In my orginal excel file database I have a P&L Line Code and the Data for each P&L Line Code. 

Then I have a mapping link with the database with the PNL Line Code. And I have 4 columns, called Level. Level 4 is detailed and 2 is not. 

So I, first, succeed on Power BI To create a matrix and make the P&L with 3 dimensions from Level 4 to level 2 to give opportunity to users to have to P&L with a lot of details or not. 
My formula was quite simple I just add to sum. 

But the problem is that, I need also to add some lines between rows. To calculate some percentage like Gross to net % or margin %. I don't know how to proceed to make this division. 

Could you help me please ? 

Thanks a lot. 

[lbendlin]

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