Smart grid has emerged in our fight against global warming by integrating renewable power sources into electrical power transmission network. We use dynamic pricing to control power demand in respond to the fluctuation in renewable power output. In dynamic pricing, the operator needs to collect information about power supply and to broadcast the latest power price. This information exchange is done through the wireless communication network within the smart grid. Wireless transmissions are error-prone and transmission errors will result in a loss of precision in demand control, which will further lead to a loss of profit to the operator. In view of the problem, this paper proposes a cooperative wireless transmission scheme called Cooperative Dissemination of Power Price and Supply (CDPS) for smart grid. The scheme exploits broadcast nature of radio channel to improve efficiency in delivering power prices to all customers, and in collecting power supply information from all renewable power sources. In CDPS, a customer that has overheard transmitted power supply information from its neighbors may help in delivering the information to the operator. Similarly, a customer that has received the latest power price may cooperatively retransmit the information to its neighbors that have not received the information. We have evaluated the performance of CDPS through random event simulations. The simulation results confirm that CDPS can indeed improve the operator's profit through more effective dissemination of information. Also, CDPS can help in reducing the amount of renewable power wasted due to a loss of reported information.