iam doing a project auto datalogger.

i have list1 ( auto /manual)

i have start time text box
and finish time test box

and cmdstart and cmstop.
my requirement is
1) when i click cmdstart and if the list1=auto
i want start time = time eg ( 8:45:01 am)
finishtime= time+3 hours (11:45:01 am)
and the cmdstop should occur at 11:45:01 am

2) if list1=manual
then only start time should be displayed
and when cmdstop clicked it should display stop time.

means if the list is auto start and finish time are of 3 hours diffrence.and if it is in manual mode finish time should be logged after clicking cmdstop.

many thanks in advace