Prevent the creation of a Quote Request list. Single Request for Single Product.

Hello/

Please help me.

To implement the functionality of the site, I need the client to be able to request a price for only one product. For this, it is necessary that he can add only one item to the Price Request list. That is, you must prohibit the creation of the Request List. And only one request for one product.
Let them be many (Requests), but I need it.

I would be VERY grateful for the help.

Sincerely, Vitaly.