excel help --- urgently
 

Hi guys,
Your help will be very much appreciated -
So here is my problem. I have a column that has 5 average values of 10
10
10
10
10
10
Now if I change the 3rd value (or 3rd row) to say 15 how do I make sure
that the average for the column remains the same (i.e. 10) but the
values in last 2 rows changes -- i.e it should be 7.5 and 7.5.
The values in the first two rows should not change and the cloumn
should appear as
10
10
15
7.5
7.5
Any help will be appreciated.

Thanks
spray2006