How to check cart "session"

[shterss]

Hi guys,

 

Now, I am adapting simple discount system in Prestashop 1.4.4 and I need little help.

 

Works like this:

- In shopping cart, a customer enters code of membership card, if code will have been verified, the customer gets little discount in %.

- a customer can use his membership card within every order he makes, BUT once per order

(membership card code is sent to another web server to be checked, and we recieve status code [1 - vip card, 2 - standard card, 3 - bad code...])

 

And my question is, what should I do to prevent a customer to submit form more times and get more discount.

I mean, is there any ID of non-placed order?

I thought about storing this ID with customer ID in database table.

 

What would you do?

 

Thanks in advance.

Edited October 25, 2012 by shterss (see edit history)