Marketpress: Quote for price

In Marketpress you can use for listing purpose or with a full e-commerce. I want to use it only for quotes. The price will change with big volumes, and the seller must negociate it.

Well, what have to be done? The user enter the how many products he want and make a quote. The seller receive the quote and respond the quote. If it can be done inside the marketpress would be great, with a history of quotes.

Thank in advance!