I have an excel sheet in which rows will look below

---------------------------------------------------------------------------*---------------

ACTIVITY STARTTIME STOPTIME TOTALTIME
---------------------------------------------------------------------------*-------------------

srikanth 11/2/2006 11.46 11/2/2006 11.48 0.02
ravikanth 13/2/2006 11.48 11/2/2006 11.50 0.02
srikanth 14/2/2006 10.48 11/2/2006 11.48 1.00
ravikanth 15/2/2006 10.30 11/2/2006 11.00 0.50


i want to merge two rows if the activities have the same name....and
add the totaltime for those two activities..that means that output
should look like below which i will save in another excel file.
-------------------------------------------
ACTIVITY TOTALTIME
----------------------------------------------
srikanth 1.02
ravikanth 0.52


can any one tell how to write a program for that using C#........