Rolling forecast - any help appreciated

[bs1991]

Hi all, in my PBIX file I currently have two tables:

• One showing a column with Year and Month (from date) with a sum of total net changes in that specific month
• One showing a column with Year and Month (from date) with actuals per month-end of that specific month

Need to find a way to calculate the remaining months (until end of 2019) based on a "rolling forecast" - e.g. May 2019 should be calculated by taking April 2019 Actuals and May 2019 Total Net Changes; calculation for June would then be the subtotal of May 2019 and taking into account June 2019 Total Net Changes. I've posted the two tables with dummy data below - the desired outcome for May 2019 would be 256 and for June 2019 it would be 258.

Any help you can provide is appreciated. Many thanks! 

[bs1991]

Please help! What makes it difficult is that the values in both tables are dynamically linked to a What-If parameter. 

Thanks for any help you can provide!