I would suggest creating a duration calculation to define the On Time time period and then compare this result to the duration between the actual delivery time and the start time of the On Time time period.

Duration =IF(OR(B29="",C29=""),"",(C29-B29+(C29<B29)))

where B29 is the start time and C29 is the end time of the duration to be calculated. Make sure that the cells are in the correct time format.