How do I position a div midway through a textblock dynamically?

I'm creating templates for a content management system. The content
for the articles will be called from a database. It is a series of
paragraphs and nothing else.

I need to have a sponsor table, containing a bulleted list, appear
midway down through the article, with the text wrapped above, to the
right, and below the sponsor table.

How can I use css to position this box to appear halfway down the
article? I'm open to specifying that it appear after, say, 3
paragraphs, or after 20% of the article, or 300 pixels below the
beginning of the article.

The only catch is that the call for the sponsor table has to occur
either before or after all of the article paragraph tags.

Oh, and the solution must work for 5.x+ browsers.

Thanks all for your help.

Dave