Having had yet another think about this.... ( you can stop rolling about on the ground in fits of laughter....) I might change the concept to to simplify the calculations given that the task could change either during the day or during the week and I don't want to have to rewrite the formulas over & over again.
Time Reason 6:30am Prestart machine 6.35am Ready 10:38am Crib 11:05am Ready 2.30pm Crib 5.45pm Service machine 6:12pm End of Day