make changes Permissions and best offer -- 3

Have a ecommerce using nopcommerce technology. Looking to add a best offer button and functionality that allows a buyer to sumit an offer for an item instead of paying the asking price. Similar to the Best office function used on ebay. Here is the scenario: Buyer browses the site and see an item they wish to purchase but would like to submit an offer to purchase of paypal retail. They click the best offer button after they have logged in, the request is sent to the seller of the site. If the seller accepts, the buyer will receive an notification and will have 48 hours to make payment. On the backend, the seller can get a minimum of what offer he will not accept, for example. seller will not accept offer less than "amount" if the buyer submits an offer less than that limit, the buyer will receive message on screen stating " your offer is too less, submit an higher offer if you wish", if the offer price is at least 1 dollar higher than the asking price, the buyer will receive notification that the offer has been accepted. The seller can turn on or off this function at any time on back end PERMISSION UPDATE Need to update the permissions on site, add more 3 or 4 more permissions you should be familIar with ASP.NET .NET APPLICATIONS