"Business Hours" Time Calculation

In my first two columns, my employees are entering standard 12-hour log-in and log-out times, such as 8:30 for log-in and 4:30 for log-out. To avoid confusion, I'd like to avoid the use of 24-hour time.

That being said, I also have employees that log in, for example, at 12:30 PM and log out at 4:30 PM.

Is there a formula for subtracting these two times, taking into consideration the whole AM/PM and 12-hour component?

Thanks in advance for your help!

As long as the AM/PM differentiation is being made in the cell, then a normal subtraction should work (multiply that result by 24 to get total hours difference, e.g. =(B1-A1)*24).

As long as the AM/PM differentiation is being made in the cell, then a normal subtraction should work (multiply that result by 24 to get total hours difference, e.g. =(B1-A1)*24).

I am not sure that would work so easily then... when you enter a time in Excel without the AM/PM designation, Excel seems to guess at which to apply...

A possibility would be to create a small drop-down list (through Data|Validation >> List) beside the times so the employee can select AM or PM and then get the formula to look at this before doing the subtraction...