Mine

    Dim teken As String
    Dim puntgezet As Boolean
    Dim isgelijk As Boolean = False

    Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click, Button5.Click, Button6.Click, Button7.Click, Button8.Click, Button9.Click, Button13.Click
        If isgelijk = True Then
            Label1.Text = ""
        End If
        Label1.Text = Label1.Text & CType(sender, Button).Text
        isgelijk = False
    End Sub
    Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
        If puntgezet = True Then Exit Sub
        Label1.Text = Label1.Text & "."
        puntgezet = True
    End Sub
    Private Sub Button17_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button17.Click
        Label1.Text = ""
        Label2.Text = ""
        puntgezet = False
        isgelijk = False
    End Sub
    Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
        Select Case teken
            Case "+"
                Label1.Text = Val(Label1.Text) + Val(Label2.Text)
            Case "-"
                Label1.Text = Val(Label2.Text) - Val(Label1.Text)
            Case "x"
                Label1.Text = Val(Label1.Text) * Val(Label2.Text)
            Case "/"
                If Val(Label1.Text) = 0 Then
                    Label1.Text = "Can not divide by 0."
                    Exit Sub
                End If
                Label1.Text = Val(Label2.Text) / Val(Label1.Text)
        End Select
        isgelijk = True
        Label2.Text = Label1.Text
        puntgezet = False
    End Sub
    Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click, Button16.Click, Button15.Click, Button14.Click
        teken = CType(sender, Button).Text
        Label2.Text = Label1.Text
        Label1.Text = ""
        puntgezet = False
    End Sub