Making an order with minus sign

[Todor Inchovski]

I was wondering if it is possible to make it so that customers can make orders from the front office with a minus sign (which means that they can order -5 quantity of some product and then it is put in the database as +products in stock)?

[Haumea]

What are you trying to achieve? 

[Todor Inchovski]

9 hours ago, Haumea said:

What are you trying to achieve? 

What I am trying to do is rework prestashop for consignation. So I need customers to be able to buy negative quantities of something (as they are returning it). The returns system is a bit odd as I read it and it does not suit my need. I hope the picture sheds light on my idea.

[Todor Inchovski]

I really need to make it so that a person has ordered (for example) 50 products, then he has sold 30 of them and is returning 20 (consignation). And I want to do it via the front office. The idea is that the person is not buying the product and it's done, but he is selling my product and then returning the remaining to me. This is what I need to achieve with the minus sign buying from the front office.

[Haumea]

I would have done it like a front controller. Where the customer types in the ID of the product and the ID of the order. Then you handle the request and modify the quantity available in stock