Calculating Times

Hello folks, I've performed a search for an answer to this but can't seem to find what I need.

I need to calculate hours worked for each shift and then have a grand total for each employee for all the shifts they have worked.

I thought I had a calculation for the individual shifts, however there is a slight problem with it - if the employee works through midnight on a night-shift then the calulation doesn't work.

And I just cannot work out how to total the daily totals into a grand total! Can anybody help?

I have attached a sample of what I am working with.