Need Formula Help ~ Converting Military Time in Time Card

Hello~

What is the best way to convert military time so that we don't get a negative number in my total column? Attached is a timecard I am working on for my employer. I have attached the file so you can see what I am talking about. Can anyone help me with formulas to fix these? I am using excel 2003.

We have 2 issues:
1. We need the time card to convert military time for one department (see examples for May 2nd & 3rd). Several overnight shifts for this department.

2. I have listed also examples on April 27th & 28th that do not calculate using regular time Example: when working a Noon shift (no military time). Or a shift that goes from 10am to 5pm.

I have no idea how to fix this so it works!

I hope I have given you enough information!

Thank you in Advance!
Jen