Table Input for products & volumes

Hi all,

Looking for some help in laying out an input sign up form. Essentially I am looking for users to sign up and provide information on what products they stock and what their weekly sales of that particular product is. I want to be able to give the user the option to put as many products in as they like.
What would be the best way of going about this? Goal is to be able to use that information to help get them a new supply deal for those products so sales volumes and products are essential.