2 Separate Ad Spaces Display Same Ad

[officiallyhiphop]

Just for fun, I've been wanting to try to design my own ads and have them appear on my site. I've got the Billboard (728x90) at the top and then I want to put a 300x250 just below the billboard and to the right side. And then you create this mega ad, that aligns up perfectly between the two ad spots.

My site isn't big enough to have a professional business manage this, so how could I make use of a plugin to get this to work? Ideally, the billboard and 300x250 ads can rotate through and display DIFFERENT ads, but if there is one "mega" ad, it will show them at the same time. Make sense?

This is just to promote posts, etc.

Thanks!