How to get a module position in the content of a blog?

I want a script (an ad code/tag) in the content, for example in the middle of the text or after the first alinea.

How to arrange that? Is there a way to place an extra position like 'easyblog-after-content' or can i place the script somewhere in a file to arange that?

I want that it happens in all the blogs. Can u help me?

Thanks!