Private Sub CheckedChanged(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) _
        Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged, _
        CheckBox3.CheckedChanged
 
   Dim cb As CheckBox = CType(sender, CheckBox)
 
   Dim str As String = cb.Text
 
   If cb.Checked Then
      RichTextBox1.AppendText(str & vbNewLine)
   Else
      With RichTextBox1
         Dim pos As Integer = .Find(str, 0, RichTextBoxFinds.MatchCase)
         If pos >= 0 Then
            .SelectionStart = pos
            .SelectionLength = str.Length + 1
            .SelectedText = String.Empty
         End If
     End With
   End If
End Sub