Calculated field - Identifying the month of inventory depletion

Hi,

I believe this is a very doable formula. Unfortunately, i was unable to come up with the answer so far. I thought someone has a quick answer for me:


(see attached)-

Column A represents our current Inventory+On order for a specific Item number (Column B).
Column C and beyond is our monthly forecasted demand.

The goal is for column O to provide the month in which we will run out of stock based on the current inventory and predicted sales.

E.g for row 2:
We have 1900 pcs in stock.
Come January, we'll only have 208 pcs left and expect to sell 656.
Therefore column O would indicate "01-Jan."

For those items where our stock will carry us beyond 1 year i would simply identify it as "1 yr +"...


Would anyone know how to automate this, so i can drag it down for all my rows and not have to manually identify the month?


Thanks!