Trouble using xaudio2

Hi,

I am trying to use xaudio2 in my C++ project to add some sound to a simple 2D space shooter I have made. I am trying to get sound effects for the shooting. Each time I shoot, the playBackAudio() function is called which contains the two lines required to play back my .wav file.

void playBackAudio()
{
        g_source->FlushSourceBuffers();
	g_source->SubmitSourceBuffer(bufferShoot.xaBuffer());
}

The trouble is, each time the sound is played, the program waits for the sample to complete before playing the next (it queues up). I tried putting the FlushSourceBuffer() in which I thought would flush the buffer and stop the sample to allow the sample to be played again.

The net affect I am after is for the sound to begin to play but if the space bar (shoot) is held down, I want the next sample to interrupt the current sample and start again (if that makes sense).

I have tried putting g_source->Stop(); followed by g_source->Start(); in the function, thinking that this may help but it made no difference.

Can anyone help?

Thanks