On FlashCall
The actions that will be performed whenever an exposed Flash actionscript function is called using the control's external API (ExternalInterface class) causing it to dispatch its FlashCall event. You can
respond to Flash actionscript function calls using the Flash.SetReturnValue action, or call Flash actionscript functions using the Flash.CallFunction action.
Flash's external API offers additional functionality compared to fscommand() by allowing any number of arguments to be passed as well as various data types.
Note: This event is only available in Flash version 8.0 or later.