Calculating and adding time

I am trying to figure out how to automatically calculate time differences for a delayed racing start time.

I have:

a rating which provides a handicap correction factor:  PHRF Tod

A Sec/ Mile correction number

A Total correction in Seconds (based on a distance)

This I figured out.

I have a set start time for the first entry at 11:00:00

I need to figure out the Start time for the delayed boats as shown in the diagram, but I don't know what formulas will do this. 

This diagram is taken from a pdf document.