Calculate the Excel value and save it in another excel in c#

Hi

I am having a excell with the following column name and value

FirstNumber                     SecondNumber             

2                                             3

4                                             6

5                                             2

When i browse  that excel, and press the calculate button, i need the resulted excel in the follwoing

FirstNumber                        SecondNumber                                Result(Addition)

2                                                 3                                                     5

4                                                 6                                                     10

5                                                 2                                                      7

Hope u understand it.

Please let me know if this is not clear.

Thanks.