Iterative calculation

I was going to tell you that you can use a calculated column BUT there is no way to tell powerbi to to run calculations in a certain order (or recursive). So the formula would be fairly complex because you have to do (in your calculated column)

- look for the maximum date available for this inventory id

- determine the stock amount

- iterate through all of the rows from that max date to current date, summing all in, out 

so something along the lines of
calcStock=
VAR thisProduct = table[product_id]

VAR thisDate = table[inv_date]

VAR maxDate=MAXX(FILTER(table;table[product_id] = thisProduct);table[inv_date])
VAR endStock=MAXX(FILTER(table);table[product_id]=thisProduct && table[inv_date]=maxDate);  table[end_day_stock_value])
VAR differential= SUMX(FILTER(Table;table[product_id]=thisProduct && table[inv_date]>=thisDate);table[output]-table[input])

RETURN
endStock+differential

(I haven't tested but SHOULD work)

Hi jsteffe 

The dax which is written by Anonymous  is correct.

One change needs to be done in it for differential