Calculating the total time of an excel logfile
 

I have a process log file that records every minute over a continuous 50 to
65 hour time frame each time the process it run. I would like to be able to
create a macro that can calculate the total time of the process run and also
allow the selection of the start cell and end cell . The time is recorded in
HH:MM:SS and is in one column of the log file spreadsheet. I can provide an
example of a portion of the log file that contains the time section.
Thanks