I am trying to take all the orders for different parts from a vendor for a
year and calculate their on-time or late delivery times.

I am having troubles when a vendor delivers early it causes a negative
number. So I need to do two things 1 find the total early deliveries and the
total numbers of days early then I need to find the total late deliveries and
the total numbers of days late.

I have used NETWORKDAYS and that works well if the shipment is on-time or
late.

Example:

Part X due date is 06/29/2007 actual receipt date 06/20/2007 = -8 or 8 days
early
Part Z due date is 06/20/2007 actual receipt date 06/28/2007 = 8 days late

What is the best way to do this?