How to place an image automatically in a div with a specific style ?

Hi all,

I'm actually searching a solution for my needs.

When I insert an image I'd like it's automatically place in a div with a specific class.
When you insert an image with FCKEditor, the html code is: < img .... src= "" /> , and in my case I'd like the html code < div class="my_class"> < img .... src= "" /> </ div>

How can I process tou do it ?

Thanks in advance