Function PRODUKTWENN(sProdukt As Excel.Range, PrRange As Excel.Range, _
                     Optional Quelle As String) As Variant
    Dim Target As Excel.Range
    For Each Target In PrRange
       If VarType(Target.Value) = vbString Then
           If UCase(Target.Value) = UCase(sProdukt.Value) Then
               If Quelle = "" Then
                  PRODUKTWENN = Target.Value
               Else
                  PRODUKTWENN = Range(Quelle & CStr(Target.Row)).Value
               End If
               Exit Function
           Else
               PRODUKTWENN = 0
           End If
       End If
    Next
End Function