Increase price per amount of combination

[washand]

Hi all,

 

Situation:

I have an online store and have multiple manufactorers throughout the world. Each with their own products and shipping terms for each product. Some of my manufactorers will ship directly to my customer. So for many products I sell, I have to apply different shipping methods. 

I couldn't really figure out how to do this with the shipping option in Prestashop so I decided to make  shipping as a product combination. For most of my products I offer standard shipping and fast shipping. Standard shipping is free but fast shippings costs a few bucks. 

 

Problem:

Whenever my customer buys more than 1 product the shipping price increases a little for some products. For example: from 2.40 to 2.50. But I can't find a way to set this up in Prestashop.

 

Question:

How can I increase the price of a combination when the customer selects 2 or more products as amount?

 

Hope you guys can help me because I am new to Prestashop!

 

Washand