How to get the changed row index in webdynpro alv ?

Dear Experts,

I have a ALV table in that one of the two col's are from date and to date. So I'm defaulting those two values based on my data base values.

Suppose in row 2 of the below snapshot, the  from date = 25.01.2014 and to date = 26.01.2014. So here my logic is todate = from date + 2(2days validity). But it should should also accept date <= 26.01.2014.

Pls help me out how to read the selected/changed row of alv table ?. I'm writing the code in ON_CELL_ACTION .

For Ex : If date is changed in 2nd row, i should read only 2nd row of the table.

Thanks

Santhosh