(Shopping Cart Into Event Calandar 1.1)

I have mambo already installed. I am starting up a shuttle business where I need to have say up to 30 trips per day. This means up to 30 different trips possible in the event calandar for a specific day. My van holds from 10-14 passengers. In my event calandar version 1.1 (Mambo Component Already Installed) I need to be able to add a cart where a Customer can choose any number of seats out of the a total amount available (10 or 14). Basically like an online store, where you have 10 or 14 of 1 item available for sale and when someone buys an item it subtracts from the amount available. (MUST SHOW NUMBER OF SEATS AVAILABLE TO START WITH ON ORDER PAGE). I want the customer to be able to purchase from 1 seat to several seats and have them go to a screen where they can put in a discount code(A MUST)and then straight to paypal, and then return the code back to my website that paymet has been made and the seat(S) subtracted or if not, the seat(s) are returned to stock ( I also want to be able to manually put back seats that are cancelled by the customer by e-mail or phone). I do not want them to have to login to make payment which I know paypal now has available. It doesn't seem like its all that difficult a cart to add, but I dont have time to make 100's of paypal buttons for work each month, otherwise I would do it as a buy now button basis. and I am not familiar with Paypals cart. I have available the following carts from fantastico. #1. agora shopping cart #2. Cube Cart #3. Zen Cart #4. Os Commerce Cart or mambo-Phpshop which I have downloaded and can be seen over at this address: [login to view URL]~soeren/mambo-phpshop/[login to view URL];Itemid=1. These can be istalled on my server within minutes. I will accept only bids that are firm and do not go over budget and you must be familiar with Php / Carts/ Paypal & Mambo. Please do not bid if you have a habit or underbidding, are placing a so called placeholder (BAD BID) or are unfamiliar with any of the items above. I need this work done ASAP. Thanks, Mark Approximate start date of the project after selecting a bid Immediate (within 1-2 days)