Sort Independent Weighted Moving Average

The following code works fine if the data is sorted from oldest to newest. I need for it to work when the data is sorted from newest to oldest. For this to work, I would need a change that works something like this: "total1 = total1 + close_(a, 1) * a" would be "total1 = total1 + close_(a, 1) * b" with "b" incremented in the opposite direction of "a". I code very infrequently & have tried a lot of different things, searched the Internet, etc. all to no avail.

For instance, with "close" data in column "I", the data sorted as follows works with the formula
"=WMA(OFFSET(I2,0,0,9,1) )" to correctly return "791.50", but the opposite sort returns the wrong number.

The correct calculation is: (807.19*9+798.38*8+793.81*7+793.06*6+776.28*5+769.48*4+773.2*3+789.01*2+793.87*1)/(9+8+7+6+5+4+3+2+1).

DateClose
11/12/2012793.87
11/13/2012789.01
11/14/2012773.2
11/15/2012769.48
11/16/2012776.28
11/19/2012793.06
11/20/2012793.81
11/21/2012798.38
11/23/2012807.18

Code:
Public Function WMA(close_)
total1 = 0
n = WorksheetFunction.Count(close_)

divisor = (n * (n + 1)) / 2

[Code] ..........