textBox1.Text = ...

    Sub CheckBox_RemoveCheckedChanged(ByVal sender As Object, ByVal e As _
      EventArgs)
        If Me.checkBox_Remove.Checked Then
            For i As Integer = 0 To TextBox1.Lines.Length - 1
                If TextBox1.Lines(i).Length >= 32 Then TextBox1.Lines( _
                  i).Remove(0, 33)
            Next
        End If
    End Sub