I need to create a purchasing control per line where it generates a purchase need considering the quantity of each product per customer versus stock availability.
As in the example of the table below I have an item XXX that is repeated in different customers with different quantities. My stock is 10un and the total demand is 21un for the first line. I have availability, but I do not need to buy the second STU-customer demand A , on the third line of 10un, STK-customer demand A-demand customer B .
Is it possible to create this type of control?
Note I work at a company that has 15mil products registered where we receive orders every day.
Example table Attachment:
ResulttableAttachment: 
I'mtryingtoadaptthiscode.whichIfoundonthissitebyMrAleGRonthesubject Adding data in cascade of a column in Access , but as it sum by date and the DB where I am working the same item is repeated in at least 15 clients the same day I am not getting it.