prestashop 1.6.0.14 create a b2b function module

Now we 're a grocery store for b2c, now we want to add some function b2b. 1. For example,1 carton 24 bottle beer, we hope to add a special field to let customer to add 1 carton/2carton/.... carton from product list or product detail page, then 24 units or 48 units..... (Budget: $30 - $250 USD, Jobs: eCommerce, HTML, PHP, Prestashop, Shopping Carts)