Value in cell calculated on previous cell value

Hi everyone!

I have the next table (example is above. First row has Headers)

The table represents number of a product units by number of months it stays in stock. So ENT shows us how much product comes into the stock. 0M - how much units remains before the end of the first month, 1M - how much units remains in stock more than 1 month but less then 2; 2M - more then 2 months but less then 3 etc.
Values in the ENT column are defined. COEF - shows the proportion of the group that will remains in stock one more month.

The values up to previous month (Columns '0M', '1M' etc) are filled manually in the source.  Values for other months must be calculated like this:  Value of the previous month * coef.  So the June value is calculated on the base of the May value, the July value is calculated on the base of calculated June value, etc.
Coef = SUM(Column n+1[2st row : actual month row] SUM(Column n [1st row : actual month - 1 row])

Here is an exemple of desired result in excel (only the values must be calculated for each month until the end of the year)
Also Sum function will be flexivel such the the bottom cell of the interval will be linked to actual month (i.e. instead of =SUM(C2:C5) there will be something like = CALCULATE(SUM(C), FILTER(Datetable, Datetable[year] = year_now &&  Datetable[month] = month_now - 1))

How do I create a measure or a column that helps me with this?