Hi,
I'm trying to add time entries using the SUM formula but I get blanks as the
result. My columns are about 20 cells long and contain anywhere from 1 to 20
entries at anyone time. I formatted all cells using [h]:mm:ss and it still
comes up blank.
Here's what I'm working with:

Date Total time
10/1/2008 4:36:33
10/2/2008 4:58:51
10/3/2008
10/6/2008
10/7/2008
10/8/2008
etc.


I want to sum up the "Total time" column. I used the following formula but
get nothing but a blank cell: =SUM(E217:E218)

Thanks,
Marta