# SumProduct in VBA in Excel 2010

Hi All
I want to use sumproduct to get a weighted average using named ranges because the data size changes from time to time.

I have this snippet:

Dim a, b As Range
a = Range("T" & Top & ":T" & Bottom)
b = Range("S" & Top & ":S" & Bottom)

Range("H5") = Application.SumProduct (a, b) / b

Top and Bottom are variables,  it crashes on the sumproduct line.

I would really appreciate someone with superior knowledge helping me out, thank you
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Commented:
what is the Top, Bottom , are they variables in your code?
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Commented:
Your syntax is incorrect the correct syntax will be...

Also assuming you have top and bottom defined and determined before coming to this part...

Option-1..

``````    Dim a As Range, b As Range
Set a = Range("T" & Top & ":T" & Bottom)
Set b = Range("S" & Top & ":S" & Bottom)

Range("H5").Value = Application.WorksheetFunction.SumProduct(a, b) / Application.WorksheetFunction.Sum(b)
``````

Option-2..

``````Dim a As Range, b As Range
Set a = Range("T" & Top & ":T" & Bottom)
Set b = Range("S" & Top & ":S" & Bottom)

``````

Both will give the same results also when you are diving by B you are not doing sum and if you want to calculate a weighted average you should do a sum of the same...

Saurabh...
0

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VBA ExpertCommented:
You can't divide by an array, which is what b is.

What would the formula look like on a worksheet?
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Commented:
you can use this
``````Public Sub b()
Dim a As String, b As String
Dim top As String, bottom As String
top = "1"
bottom = "5"
a = "T" & top & ":T" & bottom
b = "S" & top & ":S" & bottom
Range("H5").FormulaLocal = "=SumProduct(" & a & ";" & b & ") / Sum( " & b & ") "
End Sub
``````
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Author Commented:
First one worked perfectly, thanks
0
Commented:
but my solution makes it formula, so it will auto calculated when values changed

regards
0
Author Commented:
@ FarWest thanks for this, We auto create the worksheet from a database report tool and only run the macro once to organize the data. If the data changes the report is re-run
0
Commented:
aha, I see, then you are right the accepted answer is the best, and it will not have any performance impact when working on sheet
good luck
0
Author Commented:
@ FarWest - many thanks
0
VBA ExpertCommented:
Nigel

Just curious, which of Saurabh's solutions did you use?
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Author Commented:
@ Norie - the first - works well
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