sync iCal with Entourage?

When I enter calendar events into my iPhone, and then sync my iPhone with my iMac, the events show up in iCal, but not in Entourage, which I use exclusively. My iPhone calendar apparently syncs only with iMac/iCal. How can I get iCal to automatically synch with the Entourage calendar? My goal is for my iPhone to automatically sync calendar events with Entourage as soon as I synch my iPhone with my iMac. Your help greatly appreciated.