Textbox-Change event fehlerhaft

Private Sub TextBox1_Change()
If Not IsNumeric(TextBox1.Value) Or Right(TextBox1.Value, 1) = "+" Or Right(TextBox1.Value, 1) = _
"-" Or Left(TextBox1.Value, 1) = "+" Then
Beep 500, 100
Beep 1000, 100
Beep 1500, 100
Beep 2000, 100
Beep 3000, 100
MsgBox ("Bitte nur Ziffern eingeben!")
SendKeys "{BS}", Wait:=True
End If
With TextBox1
.MaxLength = 3
End With
End Sub