(vb.net) ผมต้องการตัดข้อความจาก textbox ไห้เหลือแค่ข้อความที่ต้องการเท่านั้นคับ

TextBox1.Text = ListBox1.Text
        Dim str As String
        Dim strArr() As String
        Dim count As Integer
        Str = TextBox1.Text
        strArr = str.Split("'")
        For count = TextBox4.Text To strArr.Length - TextBox5.Text
'TextBox4.Text= 7  TextBox5.Text=8
            If strArr(count).Contains("CAAA") Then

                ListBox2.Items.Add(strArr(count))

                Dim swriter As StreamWriter
                swriter = File.AppendText(TextBox6.Text)
                swriter.WriteLine(strArr(count))
                swriter.Close()

            Else
                Try

                    ListBox1.SelectedIndex = ListBox1.SelectedIndex + 1
                Catch ex As Exception

                    Timer1.Stop()
                    Button6.Enabled = False
                    Button5.Enabled = True

                End Try

            End If
        Next