Custom Weight Input

Hello everyone,

How can i let the User adds the Weight of the product during the time that he or she places the order or add to the cart?

I don't want to specify the Weight of the product in the admin panel, I want to make custom product order, so user input the price as well as the Weight of the product and then, add it to the cart, and the price will be the total of product inserted price by user, as well as the shipping cost for the item based on the inputted Weight as well as shipping method.

How can i do this?

Any expert?