''' <summary>
''' Prüft, ob der übergebene String ausschließlich aus Buchstaben besteht
''' </summary>
''' <param name="Text">String</param>
''' <returns>True, wenn String nur Buchstaben enthält, andernfalls False</returns>
'Version I
Public Function IsLetter(ByVal Text As String) As Boolean
  Dim lngCount As Long, ASCII%
  If Text = vbnullsting Then GoTo IsLetter_False
  For lngCount = 1 To Len(Text)
    ASCII = Asc(Mid(Text, lngCount, 1))
    MsgBox ASCII
    If Not ((65 <= ASCII And ASCII <= 90) Or _
            (97 <= ASCII And ASCII <= 122) Or _
             (223 = ASCII) Or _
             (228 = ASCII) Or _
             (232 = ASCII) Or _
             (233 = ASCII) Or _
             (246 = ASCII) Or _
             (252 = ASCII) Or _
             (228 = ASCII)) Then 'A-Z, a-z, oder ßäèéöü
        GoTo IsLetter_False
    End If
  Next
  IsLetter = True
  Exit Function
IsLetter_False:
  IsLetter = False
End Function
'Version II
Public Function IsLetter(ByVal Text As String) As Boolean
  Dim lngCount As Long
  Const strAllowedChar As String = _
   "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZßäèéöü"
  If Text = vbnullsting Then GoTo IsLetter_False
  For lngCount = 1 To Len(Text)
    If 0 = InStr(strAllowedChar, Mid(Text, lngCount, 1)) Then
      GoTo IsLetter_False
    End If
  Next
  IsLetter = True
  Exit Function
IsLetter_False:
  IsLetter = False
End Function
 
'Version II+
'erlaubte Zeichen als Parameter übergeben
Public Function IsLetter(ByVal Text As String, _
           Optional strAllowedChar As String = _
   "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZßäèéöü") As Boolean
  Dim lngCount As Long
'....
End Function

vb6
immer auf der Jagt nach Codeschnippseln.