Joomleague Trading

I need a automated player trading system for my XBOX 360 FIFA 12 Website. People are assigned a team and take control of their players - they can trade players between other teams to improve their team. What i need you to do is to make all trades automated so when someone wants to buy a player that offer is then sent to a page where ADMINS can put it through for it to automatically update the Team Roster according to the offer recieved. I use Joomla 1.5 and for the teams i use Joomleague 1.5.1