Calculating future forecast months using previously calculated months

Hi all

I have a custom forecast model required that uses the last 3 months of sales as part of the forecast formula.

This is required to start from the current month. IE: March is currently in progress so forecast would start from 1st March.

Forecasting March is straightforward - as prior 3 months are actuals - but how to forecast April is the issue - as it would use actuals from Jan and Feb but then also need to also use the forecasted March value.

To illustrate the calculations required, i've uploaded the excel formula's:

Also uploaded is a simple powerbi model showing the calculations and values used - with the problem being the measure "

Excel file

PowerBI File

PS: This will be implemented on a Premium model but cannot use direct query.

Thanks 

Jateen