Programmatically Changing the volume of video at specfic time interval when it is playing

I want to decrease the volume of video after a specific time interval when it is being played.I can think of using

videoView.postDelayed(new Runnable() {

    @Override
    public void run() {


    }
}, 20000);

to create an event after specified time.But for changing volume we need to get the MediaPlayer instance of VideoView(mediaplayer.setVolume(0,0)) which can be done by following listeners

void    setOnCompletionListener(MediaPlayer.OnCompletionListener l)
void    setOnErrorListener(MediaPlayer.OnErrorListener l)
void    setOnInfoListener(MediaPlayer.OnInfoListener l)
void    setOnPreparedListener(MediaPlayer.OnPreparedListener l)

but all of these listeners are called either at the beginning of video or at the end of video or when we get error.But i need mediaplayer instance at a specific time interval.How can I change the volume of video at specific time interval when it is being played?