How do I get a formula to decide on the # of cells to add up base on the
value in another cell.

For example, column A to L contains the $saving for each months of the
year from Jan to Dec. And say that savings for the first x months of the
year could be carried over from the previous year; and that x value is
reflected in column M. And I want to know the total $saving that is carried
over from the previous year. So, how do get the formula to add up the first
x number of months and put the value in column O.


Jan Saving Feb Saving Mar Saving Apr Saving May Saving Jun
Saving Jul Saving Aug Saving Sep Saving Oct Saving Nov Saving
Dec Saving # Months carried over Savings Carried Over
100 200 150 160 300 350 400 200 200 300 300 400 4 610
100 100 200 250 150 700 600 700 600 500 550 500 5 800
300 400 300 250 200 800 300 500 600 500 550 500 0 0





Thanks very much.