Calculate difference between this and previous month by product sales

[huuhaa]

Is there any easy way to do this one.

I have datasource where is monthly sales number by product. Like this one:

i have imported it on Power BI andnow i like to make custom column that calculates difference between row and row presenting previous mont for same product).

Like:

And this should be working when there is n different products and rows for x period of time.

Something like "get sales from row that has same product and date is this - month"