VS 2008 Needs guidance for a logic

Hi. I was buying some butter and bread from the Bakery. When i was done with purchasing, so did all calculations on calculator and asked for the money. I suggested him for an application, so he demanded that i want that When i put the product (lets say cake of 2 pounds) on the weight machine, so it shows me the weight and calculate its weight and a barCode on a receipt will come out, which i will paste on the product and when the customer will come to final counter, so all these barCode stickers will be scanned on barCode Reader and the values will be displayed and final receipt will be printer for him/ her.

So far, the thing which i'm not understanding is that how the weight machine will produce the BarCode Receipt? Please guide me.