Step 1: Sort Your Data Select your data range and navigate to Data ➔ Sort. Choose Item Name / Item No to group similar items together, then click OK.
Step 2: Use the Subtotal Feature With your data selected, go to Data ➔ Subtotal. Set 'At each change in' to Item Name / Item No.Set 'Use function' to SUM.Check the box for As on Stock (or your target column) under 'Add subtotal to' and press OK.