Using addEventListener for Enter and Exit frame

Question

hi , sometimes i want to set some function in specific frame in start and exit this frame
for example i have Flv player in frame 20 , i have background sound ( mp3 player ) so i want when swf goes to this frame my sound goes Off and when Exit from it and go to another frames the sound played again ...
i put these script in frame 20 :
addEventListener(Event.ENTER_FRAME,enterfunc);
function enterfunc(e:Event):void {
    trace("I started");
addEventListener(Event.EXIT_FRAME,exitfunc);
function exitfunc(e:Event):void {
    trace("will Exit");
but after test movie i see I started and will Exit runs Repeatly without stoping !!
Notice : first i put my sndChannel = soundClip.play; and sndChannel = soundClip.stop;  but my music runs over and over and finally my system Hanged and need to Restart so i use trace to see
so whats a problem ?  thanks for spending time and help me

Answer 1

kglad wrote:
// in frame 1:
function f():void{
trace("function f is executing when the playhead is in frame:", this.currentFrame);
// in frame 2:
f();
This works well For Excute Function on entering Frame Once !! thanks ...
but Only 1 More Question :
as You told me in your No.2 Replay :
I try to add some movieclip with instance name Or FLv playback with instance name and then Try to use this codes :
mymc.addEventListener(Event.ADDED_TO_STAGE, addedF);
function addedF(e:Event):void{
trace("I Start");
mymc.addEventListener(Event.REMOVED_FROM_STAGE, removedF);
function removedF(e:Event):void{
trace("I exit");
why The removedF function Works well and the addedF function not work ?!?   in fact nothing Happend on Enter This Frame but on exit i see my I exit Trace !!