But I have line level data that needs summing in the sales table. The workaround is one table of stock, one of sales and a sumif on the sales to get the stock. But now I don't have a pivot table
That’s what Power Pivot is for. Once you create the additional table and relationships as I described, you should be able to create a pivot table using data from multiple tables. No SUMIFs required. Unless I’m misunderstanding something.