Проект Калькулятор: сделать так, чтобы вводимые цифры оставались на дисплее

Public Class Calculator3
 
    Dim clearDisplay As Boolean
    Dim value1 As Double
    Dim value2 As Double
    Dim znak As String
 
 
    Private Sub DIGIT_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, Button10.Click
 
 
 
        If clearDisplay Then
            lblDisplay.Text = ""
            clearDisplay = False
        End If
 
        lblDisplay.Text = lblDisplay.Text + sender.Text
 
 
    End Sub
 
 
 
    Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click
 
        Dim result As Double
 
        value2 = Val(lblDisplay.Text)
        Select Case znak
            Case "+"
                result = value1 + value2
            Case "-"
                result = value1 - value2
            Case "*"
                result = value1 * value2
            Case "/"
                If value2 <> "0" Then result = value1 / value2
        End Select
 
        lblDisplay.Text = result
 
        clearDisplay = True
 
 
    End Sub
 
    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click
 
        lblDisplay.Text = ""
 
    End Sub
 
    Private Sub Button17_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button17.Click
        End
    End Sub
 
    Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click
        value1 = Val(lblDisplay.Text)
        znak = "+"
        lblDisplay.Text = ""
 
    End Sub
 
    Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
        value1 = Val(lblDisplay.Text)
        znak = "-"
        lblDisplay.Text = ""
    End Sub
 
    Private Sub Button14_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button14.Click
        value1 = Val(lblDisplay.Text)
        znak = "*"
        lblDisplay.Text = ""
    End Sub
 
    Private Sub Button13_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button13.Click
        value1 = Val(lblDisplay.Text)
        znak = "/"
        lblDisplay.Text = ""
    End Sub
End Class

lblDisplay.Text = ""

Dim result As Double
Dim ss As String = lblDisplay.Text
value2 = Val(lblDisplay.Text.Substring(value1.ToString.Length + 1))
Select Case znak
    Case "+"
        result = value1 + value2
    Case "-"
        result = value1 - value2
    Case "*"
        result = value1 * value2
    Case "/"
        If value2 <> "0" Then result = value1 / value2
End Select
lblDisplay.Text &= "=" & result
clearDisplay = True

value2 = Val(lblDisplay.Text.Substring(value1.ToString.Length + 1))