How to write the formula for time accounting for a work schedule

[Guest]

I am working an employee schedule and I want to find the formula to make a
cell add the amount of hours used or assigned for a given day and give me the
results in hours. Such as I schedule someone to work 1100 (11am) - 1800 (6pm)
how can I get excel to see that there are 7 hours that were scheduled and
give me the results back as 7 hours or such. I then want to take that and add
all the cells with the time and tell me the number of hours that a individual
was scheduled to work for a given week to compute my labor cost

 

[Max]

Assuming start and end times are entered in cols B & C in time format (eg.:
11:00 AM, 6:00 PM) from row2 down

11:00 AM 6:00 PM
11:00 PM 6:00 AM
10:00 PM 5:00 AM
etc

Put in D2:
=IF(C2>=B2,(C2-B2)*24,24-((B2-C2)*24))
Format D2 as General, and copy down

Col D will return the hours (duration) as numbers