DAX question about static vs dynamic calculation

*I'm simplifying the math involved and the numbers aren't really representative of what I'm calculating 

In Excel,

1. I have a calculation for a 3 Month Average Rate. The calculation takes the average of the last 3 months and returns a value. 

3 Month Average Rate = 

2. I have a second calculation for that is 3 Month Average Rate * den 

The 3 Month Average Rate stays static, but the den changes by month.

In Power BI,

1. I have a 3 Month Average Rate measure that calculates the average from the last 3 months. 

3 Month Average (%) = CALCULATE(SUM('table'num)/Sum('table'den),DATESINPERIOD('Date'[Date], [Selected Date], -3, MONTH))

2. I need to make a second measure that calculates 3 Month Average (%) * den, but the 3 Month Average (%) should be static and the den should be associated with the month it aligns to. How do I create a DAX measure that doesn't recalculate the 3 Month Average (%) by month and multiplies that by the changing den by month?