Cumulative Column But only adding if previous row was negative

Effectivly what I showed in the table, im creating this to find expected expiry stock. so for each date period any positive values(expired stock) would not be added to the next date but any negative values(remaining consumption) would be added to the calculation of next dates expired stock. The issue is it should really only be factoring whatever the previous date expired stock would be in calculating the current dates expired stock.