[Freeswitch-users] Dialing two destinations simultaneously hangup early

I need to test a case to generate following user experience .. User dials a number and when call hits freeswitch, freeswitch plays a sound file but the same time dials out to a gateway, that means user hears sound file but at the same time call is being tried by gateway and when gateway sends ring 183 or 180, Sound file stops playing and user hears ringback or any media sent by gateway . I plan to do this by using bridge application to two destinations, One is to play sound file and other to send call to gateway. But how can I hangup the call to extension which is playing Sound file, upon receiving the 180 or 183 from gateway (Second fork )..where should I look for this?