Disable format the source code

In my source code I sometimes I use special opening and closing tags like:

<table>
  <tr>
    <td>Lipsum</td>
  </tr>
{hidden_second_column}
  <tr>
    <td>Dolor</td>
  </tr>
{/hidden_second_column}
</table>

The problem is, when I switch from the HTML code to the editor, the code turns into:

{hidden_second_column}{/hidden_second_column}
<table>
  <tr>
    <td>Lipsum</td>
  </tr>
  <tr>
    <td>Dolor</td>
  </tr>
</table>
 

What can I do to prevent CKEditor from formatting the code and just leave as is?
Thank you