[Wave]

камешек в огород любителей почитать хелпы - код ваш крив.

правильно будет отловить onPlayStatus и там поделать чего угодно.

из того же хелпа:

[onPlayStatus] Dispatched when a NetStream object has completely played a stream. This handler returns information objects that provide information in addition to what's returned by the netStatus event. You can use this handler to trigger actions in your code when a NetStream object has switched from one stream to another stream in a playlist (as indicated by the information object NetStream.Play.Switch) or when a NetStream object has played to the end (as indicated by the information object NetStream.Play.Complete).