Function RPN(expr As String) As String

  Dim tokenArray() As String
  Dim stack() As String

  Dim Wert1 As Double
  Dim Wert2 As Double



  'Initialize array (removed later)
  ReDim tokenArray(1)
  ReDim stack(1)


  tokenArray = Split(expr, " ")

  Dim i As integer
  i = 0

  While i <= tokenArray.Ubound


    If  tokenArray(i) = "+" Then
      Wert2 = Val(stack.pop)
      Wert1 = Val(stack.pop)
      stack.Append(Str(Wert1+Wert2))
    ElseIf tokenArray(i) = "-" Then
      Wert2 = Val(stack.pop)
      Wert1 = Val(stack.pop)
      stack.Append(Str(Wert1-Wert2))
    ElseIf tokenArray(i) = "*" Then
      Wert2 = Val(stack.pop)
      Wert1 = Val(stack.pop)
      stack.Append(Str(Wert1*Wert2))
    ElseIf tokenArray(i) = "/" Then
      Wert2 = Val(stack.pop)
      Wert1 = Val(stack.pop)
      stack.Append(Str(Wert1/Wert2))
    ElseIf tokenArray(i) = "^" Then
      Wert2 = Val(stack.pop)
      Wert1 = Val(stack.pop)
      stack.Append(Str(pow(Wert1,Wert2)))
    Else
      stack.Append(tokenArray(i))
    End If


    i = i +1

  Wend


  Return stack(2)

End Function