Hello Clinton,

Here is User Defined Function in VBA. It can be used just like
regular Excel Formula.

It assumes that the index K is the number of entries that will b
successively summed according to your formula. The cells don't need t
be contiguous, but do need to be in the same row.

Add a VBA Module to your project and copy this code into it.

USING THE UDF

=Sum3Up(<cell Arg A, <cell Arg B, <cell Arg C, <cell Arg D, <cel
Arg E, Index_K)


Code
-------------------
Public Function Sum3Up(ByRef ArgA As Range, ByRef ArgB As Range, ByRef ArgC As Range, ByRef ArgD As Range, ByRef ArgE As Range, ByVal Index_K As Long) As Double

Application.Volatile

Dim I As Long
Dim Sigma As Double

'Summation Formula: Sigma = ( A^( k+1 ) ) * ( B / C ) * ( 1 - ( D / E ) )
For I = 1 To Index_K
'Avoid division by zero error
If ArgC.Cells(I, 1).Value < 0 And ArgE.Cells(I, 1).Value < 0 Then
Sigma = Sigma + (ArgA.Cells(I, 1).Value ^ (I + 1) _
* (ArgB.Cells(I, 1).Value / ArgC.Cells(I, 1).Value) _
* (1 - (ArgD.Cells(I, 1).Value / ArgE.Cells(I, 1).Value)))
End If
Next I

Sum3Up = Sigma

End Function

-------------------

Sincerely,
Leith Ros

--
Leith Ros
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