Hello Specialists

1. User selects a row, for example say Row#20.
2. I want to perform a calculation (formula say for example:cell value+100)
on ColumnG and ColumnH of Row 20. Starting from cell G20 till end of Column
(till last value) similarly for Column H also.
(starting from row # 10 till end of value in columns G and H)
3. How will I get handle to column G and column H of Row 20 and perform the
operation till the end of values in the column?

Thanks in advance

With regards