Microsoft is working with a company named MediaCart to serve up ads to supermarket shoppers based on both their shopping lists and past purchases, reports The Associated Press.

Beginning in the second half of 2008, Microsoft and MediaCart will roll out the test phase, targeting shoppers with ShopRite loyalty cards. Cardholders will be able to visit a website and plan their shopping list that will then appear on a cart-attached screen when they get to the store and swipe their card.

The screen will display the price of items that shoppers place in the carts and a running tally of the total; moreover, ads, coupons and incentives will also be displayed as shoppers walk around the store.

The instant-feedback nature of such incentives will give advertisers real-time results on which prompts worked and which didn't.

Micrsoft's ability to move into aggressive planning of this program was reportedly jump-started by the acquisition of aQuantive last year.