FIFO HELP! Iterative macro, How can it be computed

[amruta]

input has billed qty(in) and qty sold (out). I need to split the qty sold based on order it is billed and apply the rates accordingly. The billed qty ikey is Food Name, Food Type, Carrier and Period, but the qty sold is by Food Name, Food Type and Period, refer the color coding to understand the expected solution. See attached sample workflow and in excel is the expected solution.