VB录入字符时限制格式和字符

如何在录入MAC地址的时候,限制格式和字符
我想在 VB 里录入 AB-33-21-00-88-12
  这样的 MAC 地址,
  如果 限制 录入的 字符是 16进制内的 从0-9, A-F
  而且不用 录入 中间的 -
Private Sub Text1_KeyPress(Index As Integer, KeyAscii As Integer)

Text1(Index).MaxLength = 2
'AB-33-21-00-88-12
    Dim L As Long
    L = Text1(Index).SelStart
    If L < 2 Then
        If KeyAscii = 8 Then Exit Sub
        If Not ((Asc("0") <= KeyAscii And KeyAscii <= Asc("9")) Or (Asc("A") <= KeyAscii And KeyAscii <= Asc("F")) Or (Asc("a") <= KeyAscii And KeyAscii <= Asc("f"))) Then
            KeyAscii = 0
        Else
            KeyAscii = Asc(UCase(Chr(KeyAscii)))
        End If
        If L = 1 And Index < 5 Then Text1(Index + 1).SetFocus
    End If
End Sub

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