Making a "block" plugin

Hi -- is there a way to tell FCKEditor not to apply formatting to a chunk of HTML within the editor?

I'm trying to make a plugin that will insert a template tag for our CMS into FCKeditor. An example of a template tag is: {% signup_form %}

When inserting into the editor, we wrap it in a div so we are able to style it. The plugin inserts code like <div class="templatetag">{% signup_form %}</div>. I don't want this div to be editable -- the user shouldn't be able to edit the text, change the alignment, font size, NOTHING.

This is how it looks:


I should not be able to type into the div like this:


Also, I'd like to make the whole div "clickable", like the image/table toolbar item (when you click it, it selects the whole table).

Is there a way to make my template tag div act as it's own "block" element?

Thanks!