Calculating current month balance divided by the previous month of the above range

[willianvbuss]

I need help to do the calculation according to the attached image. In summary, I need to calculate the balance for a given range in the current month by the balance for the previous month in the range above.

Important: i need in a line chart, not in pivot table. In pivot table it's already done, using:

=sum(SomaSaldo)/above(Before(Sum(SomaSaldo),1,ColumnNo()))

But it's not working with the line chart.

Thanks.