Cumulative substraction

Hello, I am trying to apply a cumulative amount but I have problems with Power Query.

In first table X_Previsionnel, I have the quantity (column need) that will be consumed for each of my articles. I go up to 3 days in the future (we don’t care about quantities in the past, that’s the delay)
In second table X_Stock_Metal, I have the status of my stocks of the day before, for each of my 7 articles.

I would like to calculate a forecast stock, from the previous day’s stock and subtract the needs corresponding to each item for my current day. Then start from this new level of stock and subtract the needs of tomorrow (always for each of my articles), and the same for the day after tomorrow.

Thanks for your help!