Calculating Costs over varying shifts

This might be a good starting point :
http://cpearson.com/excel/pricing.htm
and search for "progressive pricing"

This can be done but it depends on what information you have.

Do you have start date and end date or just a start time and end time.

I see you have a night shift, will you have tasks that start one day and end the next? What's the longest stint you might have, e.g. could it be 10:00 one day to 06:00 the next?