how can i wait until my sound completely played in XNA and then i do other things?

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XNA4.0

Hello friends I'm using this code to play sounds in mp3 and wav format in xna, I don't know how i can find out if the sound is completely played or not?
//Putting a sound in buffer for playing
fncPutAWavSoundOnBuffer(1);
fncPutAWavSoundOnBuffer(2);

public bool songbuffer = false;
       public bool soundbuffer = false;
       public Song CurrentSong;
       public SoundEffect CurrentSound;
       public void fncPutAMP3SoundOnBuffer(int code)
       {
           CurrentSong = content.Load<Song>(GivemeSoundFileNameByCode(code));
           songbuffer = true;
       }
       public void fncPutAWavSoundOnBuffer(int code)
       {
           CurrentSound = content.Load<SoundEffect>(GivemeSoundFileNameByCode(code));
           soundbuffer = true;
       }

public string GivemeSoundFileNameByCode(int code)
        {
            string BaseDirectory = ".";
            switch (code)
            {
                case 1:
                    {
                        return BaseDirectory + "\\StartPage\\Sounds\\ButtonMouseOverSound";
                    }
                case 2:
                    {
                        return BaseDirectory + "\\StartPage\\Sounds\\ButtonClickSound";
                    }
                case 3:
                    {
                        return BaseDirectory + "\\AddNewWordsPage1\\Sounds\\mp3PleaseWiteYourWordHere";
                    }
                default:
                    {
                        break;
                    }
            }
            return "";
        }

protected override void Update(GameTime gameTime)
     {
         // Allows the game to exit
         if (GamePad.GetState(PlayerIndex.One).Buttons.Back == Microsoft.Xna.Framework.Input.ButtonState.Pressed)
             this.Exit();
         PlaySound();
         base.Update(gameTime);
     }

public void PlaySound()
      {
          if (clsMyDefenition.soundbuffer)
          {
              clsMyDefenition.CurrentSound.Play();
              clsMyDefenition.soundbuffer = false;
          }
          if (clsMyDefenition.songbuffer)
          {
              MediaPlayer.Play(clsMyDefenition.CurrentSong);
              clsMyDefenition.songbuffer = false;
          }
      }