Need to add cells depending on other cell.

Hi
I need to add few cells.
But problem is My number of cells depend on other cells value.
E.G
I want to add values from column AR
depending on value in cell P2

Right now m using
=(SUMIF(AQ$5:AQ$469,AX4,AR$5:AR$469))/P$2

but unsuccessful

suppose if P2 is 2
so i will add AR5 and AR13
suppose p2 is 3
thn I will add AR5 AR13 and AR21 and so on....


Can some one help.?

Thanks in advance

Cross-posted (and answered there 25 minutes ago...)

http://www.mrexcel.com/forum/excel-q...ther-cell.html