Private Sub CountChars(ByVal str As String)
    Dim i As Integer, zeichen As String, zeichenindex As Integer    
    For i = 1 To Len(str)
       zeichen = Mid$(str, i, 1)
       zeichenindex = Asc(zeichen)
       charcounter(zeichenindex) = charcounter(zeichenindex) + 1
    Next i    
End Sub