Hallo ladies and gentle men,

I have two columns, A and B. I want to have a third
column, C, by multiplying column A and B in an inverse
order. That is to mean C1=A1*B1, C2=A2*B1+A1*B2,
C3=A3*B1+A2*B2+A1*B3, C4=A4*B1+A3*B2+A2*B3+A1*B4, etc. One
friend in this forum provided me the following subroutine.
I just copied it, paste it in VBE of the sheet I am
working on, and saved the workbook. When I want to do the
calculation in C1 by pasting the "doit" formula given
below, what I get is an error (#Name). What is the
problem? Please see the subroutine and the formula and
help out. Is there a non-macro version of solving this
problem?

Thanks

The subroutine is
Function doit(N, rangeA As Range, rangeB As Range)
Dim tempA(10), tempB(10)
j = 1
For Each cell In rangeA
tempA(j) = cell
j = j + 1
Next
j = 1
For Each cell In rangeB
tempB(j) = cell
j = j + 1
Next
mysum = 0
For j = 1 To N
mysum = mysum + tempA(j) * tempB(N - j + 1)
Next
doit = mysum
End Function

and the formula is

=doit(ROW(),$A$1:INDIRECT("A"&ROW()),$B$1:INDIRECT ("B"&ROW
()))