title: Prestashop voucher system
body: <p>The problem I am having is related to voucher codes.
  By default, Prestashop will apply a discount of a particular product to the total of the entire cart. For example, if I have 3 products in my cart, all priced at £100, the total sum of the cart is £300.
  If i have a voucher for a total value of £200 that is valid for only 1 of the 3 products in my cart, the behavior I want to achieve is that Prestashop will recognise that the voucher is valid for only one product, and rather than deducting the £200 voucher total from the cart total (essentially applying the remainder of voucher credit to the other two, non applicable items), it will deduct only the amount of all applicable items (in this case, £100), and some how create a new voucher for the remainder of the credit.</p>
  
  <p>Hopefully this makes sense and many thanks in advance for any help offered.</p>
  
  <p>Cheers</p>