Chat system

I am creating a website in asp.net, which require chat. It is online buying an selling new items, the seller has to be a part of our website, that is he has to pay and then he can list upto 6 items at one time. From the seller my account>>> 1)The seller click on I want to go online. 2) Then he check on the check boxes out of 6 items, to which he wants to be online. (see picture 2) 3) Then the seller click on go online.... The seller will be online on those which he check to be online. The seller also can go OFFLINE from chat by clicking on go offline button, if he wishes to. (by clicking on go offline button, he won't log off from his account). From the user point of view, the user sees seller as online on his listing... he want to know more about shipping and handling? he click on chat after filling some details of his own like location. (see picture 1) ******The seller receives 4 chats ***** suppose the seller receives 4 chats, whoever, logged in first will be there to chat with the seller. Rest would be in queue, with there questions viewable to seller although he haven't chatted. at the buyers ends if he is in queue, he will be given the message about his position in queue. The seller has the right to reject the user's question if he sees its asked many times, from the queue itself by click on button reject (see picture 2). The seller can also block the user by clicking on block button (see picture 2) The seller can also pull any chat from queue (see picture 2) when the seller pull the chat from queue a message will appear to confirm that if pulled, the current chat will lost and the rest queue will be re-postioned. Please give your best bid. Thanks, we will think about your bids. Thanks