Apologies if this has already been asked. I have one "Master" page in excel with a running inventory. Subsequent pages in that workbook are fulfilled orders, and I've set it up so that each page's inventory is the same - in other words, cell B15 in Master is the starting count of Type B Brochures, cell C15 in Master is the current count after orders are fulfilled. C15 in each order sheet is the number of Type B Brochures fulfilled. How do I deduct the value in all order sheets from the Master and can I have it auto-update when I add a new order sheet?