Dependency on prior month calculated metric

[CuriousGeorge]

Hi, 

I have a question, and this is a relatively easy calculation on Excel. However, my methods do not work on Qlik Sense and hope to get some ideas on this forum. To make it easier to understand, I have simplified the question and metrics.

So I have a pivot table displaying monthly snapshot (columns) and calculated metrics on each row. I need to calculate ARR for each month, and each month is dependent on the prior month metric + some current month metrics. 

I think I need to use some recursive methods, or whatever method that is the best way to calculate ARR metric.