D3 is the a cell holding a total, d12 threw d428 at every 8th interval to deduct from the total in d3.

=D3-(D12-D20-D28-D36-D44-D52-D60-D68-D76-D84-D92-D100-D108-D116-D124-D132-D140-D148-D156-D164-D172-D180-D188-D196-D204-D212-D220-D228-D236-D244-D252-D260-D268-D276-D284-D292-D300-D308-D316-D324-D332-D340-D348-D356-D364-D372-D380-D388-D396-D404-D412-D420-D428)