|A simple way could be something like:|
1) Time In 1/27/11 8:00
2) Time Out 1/27/11 12:00
3) Time In 1/27/11 12:30
4) Time Out 1/28/11 1:45
6) Lunch 0:30
7) Total Hours 17.25
Column B Cells 1 - 4 are formatted as DATE & TIME
Cell B6 and B7 are Custom format [H]:MM, the square brackets are required.
The formula in Cell B6 is: =SUM(B3-B2)
The formula in Cell B7 is: =SUM(B4-B3)+(B2-B1)
As you can see from my example, crossing over MIDNIGHT can be done.
The format in cells B6 & B7 are the key to getting the correct number of hours.
Doing Date & Time math in Excel can be very tricky.
If you plan on doing Date & Time math then I would advise you to read the below link for a complete explanation of how Excel deals with Dates and Time, it is a great resource.