Validating checkboxes using VB.NET

I'm very beginner in Programming, now I'm learning with VB.NET. Here is the scenario, I have 3 checkboxes and 1 textbox. When Checkbox1 and Checkbox2 are checked then Text in the textbox becomes 1 else textbox becomes 0.

This is my code :

Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged,
    CheckBox2.CheckedChanged

    If CheckBox1.Checked And CheckBox2.Checked Then
       TextBox1.Text = 1
    Else
       TextBox1.Text = 0
    End If
End Sub

This is working based on the scenario but when I checked all three of them, textbox doesn't change 0 and still 1. How do I solve this ? Last time I tried to change my code :

Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged,
        CheckBox2.CheckedChanged

        If CheckBox1.Checked And CheckBox2.Checked Then
           TextBox1.Text = 1
        Elseif CheckBox1.Checked And CheckBox2.Checked And Checkbox3.Checked Then
           TextBox1.Text = 0
        Else
           TextBox1.Text = 0
        End If
    End Sub

Or Is it possible to grouping all checkboxes in an array ? then I will count if checkboxes checked more than 2 then ... {do something}.