Shopping cart software for digital files with unique barcodes.

Hello,

I am looking for shopping cart software that will allow the creation of digital file product, without needing to load-up the file on my server until the product is purchased by a customer. Once a customer purchases a quantity amount, I will manually load up the digital file and an email will be sent to the buyer with the download link.

The reason for this is that the digital file is the same but each file has its own barcode.

If that is not possible, I can upload the digital files ahead of time, but the software must recognize that each digital file is unique and the file can only be downloaded by one buyer. So if I have a quantity if 20 digital files in stock, the software will keep track of stock and will only send the files once to the buyer and then remove it from the inventory.

I can do this with most shopping carts by creating one product and uploading just one digital file with its own barcode and repeat the process for each unique digital file, but I don't want to have, lets say 20 products that are the same in one category.

I need to have one product listed in that category, where the customer can purchase an amount of that product, but if the customer purchases a quantity of 5, they will receive a download link after purchase, for 5 individual products with a different barcode.

I would appreciate any help on finding something that will fit my needs and I hope this is clear enough understand.