Excel - User defined function getting is being called even when not active - vba

Question

I have a user defined function in excel. The function contains Application.Volatile at the top and it works great.
The problem I am experiencing now is that when I have the workbook open (lets call it workbook 1) together with another workbook (call it workbook 2), every time I make a change to workbook 2, all cells in workbook 1 that call this UDF gets a #VALUE! error.
Why is this happening?
I hope I provided enough info. If not please let me know.
Thanks
David
Hi guys, thanks for the help.
Sorry about that... here is the code:
Function getTotalReceived(valCell As Range) As Variant
Application.Volatile
If ActiveWorkbook.Name <> "SALES.xlsm" Then Return
Dim receivedWs As Worksheet, reportWs As Worksheet
Dim items As Range
Set reportWs = Worksheets("Report")
Set receivedWs = Worksheets("Received")
Dim myItem As String, index As Long
myItem = valCell.Value
Set items = receivedWs.Range("A:A")
index = Application.Match(myItem, items, 0)
If IsError(index) Then
Debug.Print ("Error: " & myItem)
Debug.Print (Err.Description)
GoTo QuitIt
End If
Dim lCol As Long, Qty As Double, mySumRange As Range
Set mySumRange = receivedWs.Range(index & ":" & index)
Qty = WorksheetFunction.Sum(mySumRange)
QuitIt:
getTotalReceived = Qty
End Function

Answer 1

Your problem is with the use of ActiveWorkbook,ActiveWorksheet or ActiveCell or other Active_____ objects in your UDF. Notice that Application.Volitile is an application-level property. Anytime you switch sheets, books, cells, charts, etc. the corresponding "active" object changes.
As an example of proper UDF coding practice I put together this short example:
Function appCallerTest() As String
Dim callerWorkbook As Workbook
Dim callerWorksheet As Worksheet
Dim callerRange As Range
Application.Volatile True
Set callerRange = Application.Caller
Set callerWorksheet = callerRange.Worksheet
Set callerWorkbook = callerWorksheet.Parent
appCallerTest = "This formula is in cell: " & callerRange.Address(False, False) & _
" in the sheet: " & callerWorksheet.Name & _
" in the workbook: " & callerWorkbook.Name
End Function

Answer 2

Function getTotalReceived(valCell As Range) As Variant
Application.Volatile
Dim index, v, Qty
v = valCell.Value
'do you really need this here?
If ActiveWorkbook.Name <> ThisWorkbook.Name Then Exit Function
If Len(v) > 0 Then
index = Application.Match(v, _
ThisWorkbook.Sheets("Report").Range("A:A"), 0)
If Not IsError(index) Then
Qty = Application.Sum(ThisWorkbook.Sheets("Received").Rows(index))
Else
Qty = "no match"
End If
Else
Qty = ""
End If
getTotalReceived = Qty
End Function

Answer 3

You actually have 2 errors in your function. The first was partially addressed by Mr. Mascaro - you need to use the Range reference that was passed to the function to resolve the Workbook that it is from. You can do this by drilling down through the Parent properties.
The second issue is that you are testing to see if Application.Match returned a valid index with the IsError function. This isn't doing what you think it's doing - IsError checks to see if another cell's function returned an error, not the previous line. In fact, if Application.Match raises an error, it is in your function so you have to handle it. I believe the error you need to trap is a type mismatch (error 13).
This should resolve both issues:
Function getTotalReceived(valCell As Range) As Variant
Application.Volatile
Dim book As Workbook
Set book = valCell.Parent.Parent
If book.Name <> "SALES.xlsm" Then Exit Function
Dim receivedWs As Worksheet, reportWs As Worksheet
Dim items As Range
Set reportWs = book.Worksheets("Report")
Set receivedWs = book.Worksheets("Received")
Dim myItem As String, index As Long
myItem = valCell.Value
Set items = receivedWs.Range("A:A")
On Error Resume Next
index = Application.Match(myItem, items, 0)
If Err.Number = 13 Then GoTo QuitIt
On Error GoTo 0
Dim lCol As Long, Qty As Double, mySumRange As Range
Set mySumRange = receivedWs.Range(index & ":" & index)
Qty = WorksheetFunction.Sum(mySumRange)
QuitIt:
getTotalReceived = Qty
End Function