How do I do this: coupon ? Hidden product ?

Let me preface this with the fact that I am a software engineer that knows perl and mysql (I can hack and whack at PHP but far from an expert).

This is a feature that I think should exist but probably does not.

What I want to do is offer a special deal to people that click on a paid ad (let's say adwords).

I have javascript that will generate a count down time and then redirect to the front page if they don't act on the "deal" in the allocated time.

What I want to do, if they order in the next 10 minutes, is give them two free products. I can obviously use the adwords API to turn ads on and off and encode the url (with some type of time or code).

Without getting into details of the product, basically I could give them a discount code but it will be more profitable to give them some extra product, a bonus item, free shipping, etc.

I would then like to display on the page, the deals that are on our front page except, each one will have an additional item that shows the 2 FREE items if they order now.

I could then make it so if they time out and are redirected, they can not go back to the page with the deals.

I could easily write my own software to handle this special page, but I would rather everything be done though the same system.

Any tips on how I should do this ? I.E. coupon, hidden product, etc.

P.S. Long before the shopping channels (30 years ago) I had a successful flea market business and would draw massive crowds and sell out (many cases of) product in minutes using this method.

I want to add that I just found a plug in that will somewhat do what I want:
http://www.zen-cart.com/index.php?main_page=product_contrib_info&cPath=40_60&products_id=1844

It does not have the all important "in the next 10 minutes" element.

I want to make sure paid clicks have a high conversion rate ... and based on my experience this "must act now" will help sales and is probably a good feature for anyone using zen cart to sell products if they do any form of advertising.