how to create database which saves contents of listbox and show listbox contents in text boxes when selected

hello,

I am a very beginner programmer. In my code I have create a basic add/sub feature, three textbox and two buttons( +,-). Two o f the textboxes will accept a value, when one of the buttons(+,-) is clicked the result shows up in the third textbox and then the display button will show it in the list box. I then am trying to code a listbox where I can select an line from the listbox, have it show up in the textboxes I created and modify it and save it back to the listbox/database...

for example 1+2=3 is in listbox, when you click this line in the listbox it will show 1,3 in the textboxes and you can then click the subtract button to modify it and save results back in textbox/database.

here is the code I wrote

Public Class Form1
    Dim c As New MathOp
    Dim d As New MathOp2
    Dim Num1 As Integer
    Dim Num2 As Integer
    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        Num1 = c.add(CInt(TextBox1.Text), CInt(TextBox2.Text))
        TextBox3.Text = Num1
        'TextBox3.Text = c.add(CInt(TextBox1.Text), CInt(TextBox2.Text))
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Num2 = c.subt(CInt(TextBox1.Text), CInt(TextBox2.Text))
        TextBox3.Text = Num2

    End Sub
 
        End Sub

    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        Dim showtext As String
        If TextBox3.Text = Num1 Then
            showtext = (TextBox1.Text & "+" & TextBox2.Text & "=" & Num1)
            ListBox1.Items.Add(showtext)
        ElseIf TextBox3.Text = Num2 Then
            showtext = (TextBox1.Text & "-" & TextBox2.Text & "=" & Num2)
            ListBox1.Items.Add(showtext)
        End If
    End Sub

    End Class
THanks so much for any help