How can I add periods of production time between maintenance events such as when filters were changed? I collect the production start and stop times and when the filters were changed:

Date Start Stop Maintenance
3/08/02 6:00 AM 2:30 PM 12:50 PM
3/09/02 6:00 AM 12:30 PM None
3/10/02 No Production
3/11/02 6:00 AM 2:00 AM 6:00 AM
3/12/02 6:00 AM 2:00 AM 1:00 PM
3/13/02 6:00 AM 2:00 AM 4:00 PM
3/14/02 6:00 AM 2:00 AM None
3/15/02 6:00 AM 2:30 PM 2:00 PM
3/16/02 No Production
3/16/02 No Production
3/17/02 6:00 AM 2:00 AM 1:00 AM

I can make a big nested IF-THEN, but there must be a better way.