If you put =D4-C4 in column E, for example, you can use a formula like
=SUM(E4:E34) to sum the times in column E. Excel will "roll over" at 24
hours when displaying the result. Thus, thirty hours, 30:00:00 will be
displayed as 6:00:00 (30 hours - 24 hours = 6 hours). To prevent this and
force Excel to display the number of hours, (e.g., 30 hours displayed as
30:00:00) use a custom number format of [hh]:mm or [hh]:mm:ss. The square
brackets [ ] prevent Excel from rolling over at 24 hours. (Note that this
affects only the displayed value, not the actual value of the cell.
Regardless of the display format, thirty hours is the actual value of the
cell.)
If you are going to use the total number of hours in a calculation (e.g.,
Income = TotalHours * Rate), you must multiply the total hours by 24. For
example,
=24*TotalHours*Rate
Format that cell for General or Numberic, not Time.
See
www.cpearson.com/Excel/DateTime.htm for much more information about
working with dates and times in Excel.
--
Cordially,
Chip Pearson
Microsoft MVP - Excel, 10 Years
Pearson Software Consulting
www.cpearson.com
(email on the web site)