title: Access query to subtract first row of sales demand from static inventory table. Second row of sales demand subtracted from result of first row
body: <p>I have the following 2 main tables &quot;Sales&quot; and &quot;Inventories&quot;  I need to subtract sales from inventory in the first row and then use the result &quot;RemInv&quot; to subtract from the next row.  This would be based on Product_ID and CRDate.  Trying to get inventory after each sales and determine at what date the inventory goes negative.</p>
  <p><img src="https://i.stack.imgur.com/Nm8cq.png" alt="2 Main tables Sales &amp; Inventories with resultant table sales_2" /></p>