sales form for group deals

I'm looking for a script that will allow me to sell group deals on my site. Front end: I have a form to process credit cards in my country. We'll need to edit it to offer paypal as an alternative, and count down how many items are left. For example, I'll input that we have 100 items to sell, and it will reduce that number by one for every sale. We'll also want it to have a countdown timer to when the deal is over. When the deal concludes or stock is finished, the form will disappear and show a message instead. On the backend, we'll need information about all buyers to be imported into a spreadsheet on google docs. The buyer will automatically receive an email with a voucher for the purchase. That voucher will have both graphic and static content, and a code generated by the script. The script should be compatible with my linux/php server, and not be database driven. I'll probably display it as an Iframe on the sale page (unless you have a better idea.) You'll show me where to change the variables for each sale we do.