How to stop sound file

programming flash
1

hi -
in a movieclip I have several buttons which play different mp3 files.
How can I manage that one file stops as soon as I click on another one?
Right now there is an overlapping of all sound files.

Here is the code:

soundobjekt = new Sound(this);
soundobjekt.attachSound("Socializtion");
soundobjekt1 = new Sound(this);
soundobjekt1.attachSound("Externalization");
 
socialization.onPress = function(){
 soundobjekt.start();
 
}
externalization.onPress = function(){
 soundobjekt1.start();
      
}

soundobjekt.stop(); does not work.