To sum times you usually use Excel built-in function SUM. If you have three cells A1, A2 and A3 formatted as time (hh:mm), and you have :
A1 = 02:30
A2 = 10:15
A3 has the formula: =SUM(A1:A2)
then A3 will have the correct values of 12:45.
However if your total times are greater than 24 hours then things get tricky.
If you have :
A1 = 15:30 and A2 = 10:15 then A3 will have 01:45 instead of 25:45. I.e. any hours beyond 24 hours are dropped.
To retain the hours beyond 24, you have two alternatives:
1. If you want to convert the hours beyond 24 into days then use this cell format : dd:hh:mm. The total in the previous example will be 01:01:45 ( 1day , 1 hour and 45 minutes)
2. If you want to keep the hours beyond 24 as is then use this cell format :[h]:mm. The total in the previous example will be 25:45.
In both cases the formula will remain as it is. Only the cell format differs.
See another example below:
More posts on time:
http://www.exceldigest.com/myblog/2009/02/08/how-to-add-or-sum-times/
http://www.exceldigest.com/myblog/2008/12/04/how-to-create-a-custom-time-format/











How to search for a text in a formula or a comment
It may be interesting to know that the Find option in Excel Edit menu is not limited to finding cell values, but it can also be used to search for text in a formula or a comment.
To search for a text in a formula follow these steps.
1. In the Edit menu click Find.
2. The Find and Replace window will be shown.
3. There are three combo boxes that are labeled “Within”, “Search” and “Look in”. If those combo boxes are not shown then click on the Options command button to expand the “Find and Replace” window.
4. Click on “Look in” combo box and select Formulas.
5. Click on the Find All command button.
6. All cells that have formulas, and that contain the text searched for will be listed at the bottom of the window.

Notes:
1. You can search for text in a comment in a similar way by changing your selection in the “Look in” combo box.
2. You can specify to search within one worksheet or the entire workbook, depending on your selection in the “Within” combo box..
Applies to Excel 2003