How can I add the times of individual phone calls to get the total time spent
calling from a particular phone number? The phone call record has been
placed on an Excel spreadsheet in the hour:minute:second format and sorted by
phone number with associated length of call. I've formatted the column for
times. In the next column, cell G22, I've placed the formula =SUM(F4:F22);
the formula returns zero.

Why won't the formula total the time?

Thanks.