Excel help

I have an excel sheet that is used for tracking individual legs of a relay race. This involves calculations of time to show ahead or behind an estimated pace. The sheet has evolved over several years of a particular race and each year I try to improve it a bit. I am having problems and could use help from someone a bit more experienced with excel then I am. The specific problems are highlighted in yellow in the sheet and I will provide some details here. Column G should check if the leg of the relay will be completed at night. This seems to be working for anything after midnight but I need it to be based on the adjusted sunset which is in C8. Column N and O, need to have the format adjusted to have the time in hh:mm:ss and not roll to the next day. Ex. I want to enter a number in column O that matches what our stop watch says which could be 27:32:00 for example. Column T & U are meant to calculate ahead of behind time of the estimated pace. If I enter a time under the estimated pace I need Column T to show that time in red (a negative time) for the individual runner and in Column U for the series of six runners.