Coupon Code with expiration limits

Need to things done! 1st task: Need a code script that will issue a coupon code valid for a certain amount of uses. here is an example page: [login to view URL] ______________________________ It is to be used for our site [login to view URL] and the coupon script should be placed on this page: [login to view URL];catid=5&subcatid=69&cityid=322&lang=en The coupon should work like this. If a person selects the buying option: $69.00 for 12 posts ( Super Value) then the system will bill the person accordingly using [login to view URL] and once a successful IPN payment has been received, then the system will generate a coupon code that will expire after 11 more uses. ( or a predetermined amount that we set) Coupon code will not be valid unless a successful payment has been processed. very important!! Once the coupon is issued to a buyer,,,they can come back to the site to post a new ad instead of having to pay again, all they need to so is simply enter the coupon code in the coupon code box and it will bypass the payment required and post the ad. 2nd task: We need to make changes to our edit screen to allow upgrade purchases after the sale. please see attached files for both task Please do not bid more then $50 that is the total budget for this project. We need this done within 24 hour, thank you