Tracking order dates.

My question seems simple but so far nobody can solve it. Column A is date ordered. Column B is date that the order is expected to arrive-this has been programmed for 3 weeks after date ordered. I need 2 things please. First if the expected date arrives, the cell must highlight automatically (conditional formatting). This will flag me to follow up late orders.
Second, if I check the check-box in Column C, it must override or reverse the conditional formatting of Column B, because by checking the box, it means that the order has arrived. Hope I've explained this properly.

Problem solved, thank you very much.