Function TrueChars(myString As String) As Boolean
Dim I As Integer
TrueChars = True
For I = 1 To Len(myString)
    Select Case Asc(Mid(myString, I, 1))
        Case 48 To 57  '0 to 9
        Case 65 To 90  'A to Z
        Case 97 To 122 'a to z
        Case Else
            TrueChars = False
            Exit For
    End Select
Next I
End Function