Putting advertisements between every n posts

Hi,
First off, great theme! I was able to make minor modifications to the theme to get the output how I wanted it. Modifications were simple steps such as relocating the feature image and wrapping the description text to the right (image float left css class).

I am looking at inserting advertisements into my feed, but not in the header,footer,sidebar locations. I am using the 2 column magazine layout where I have two posts side by side. I would like to be able to drop in an ad between every “n” number of posts. Ex, between posts 2 and 3, drop an advertisement. This advertisement would fill in the spot where post 3 should have been displayed, and post 3 is bumped one location.

Simple Example:
Normal Layout:
Post 1 Post 2
Post 3 Post 4

Requested Help:
Post 1 Post 2
Post 3 AD
Post 4 Post 5

Ideally, I would like the random advertisement to repeat every x number of posts, or even be hardcoded to only appearing between posts number x and y.

Maybe a special widget area that will repeat itself in the theme, or publish itself between posts x and y?

I understand this is a little bit of work, and if this request were to show up in the paid version, I would be more than happy to purchase a single copy version for my site.

Thanks again