Track status of Microsoft TTS output to wav file

Question

I'm trying to track the status of my applications TTS output to a wav file. When speaking the text (to the speaker) the expected events (StartStream, Word, EndStream) are fired, however, no events are fired when outputing to a wave file.

SpVoice vox = new SpVoice();
vox.Word += VoxWord;             // Handle word processed event

SpFileStream voxStream = new SpFileStream();
voxStream.Open(@"c:\test.wav", SpeechStreamFileMode.SSFMCreateForWrite, false);

vox.AudioOutputStream = voxStream;
vox.Speak("Hello World. Please track my status!", SpeechVoiceSpeakFlags.SVSFlagsAsync);

Is it possible to asynchronously know the status of TTS output to wav?