1. In PivotTable Field List drag a data field into Values area, in the example presented drag the Quantity Field.
2. Select a cell in the second Quantity Field, right click and select Value Field Settings.
3. Select Show Values as tab, select from Show Values as dropdown list Running Total in,
from Base field select the Row label field, in the example presented select Years field,
click Number Format button and select the desired formatting and click OK twice.