Preventing editing of "special" lines / paragraphs / divs?

Hi everyone,

while working on my own little blog / cms system I thought that it would be a cool feature to have some kind of module system.

Before delivering html to the browser the html code will be parsed for special keywords, which is then replaced by the html code generated by the module.

Example:

[module_slideshow("images/Winter2012")]

generates html code for a slideshow which displays images from folder "images/Winter2012".

My question: Is there any way to handle such special lines as a block element which can be removed as a whole but cannot be edited (missing characters, path, etc.)?

Thanks for any hints

Tom