Problem with btn action ( inside/outside )

programming flash
1

Hi there

i am facing little problem here

first take a look at this action


on (release) {
 if (_root.currMovie == undefined) {
  _root.currMovie = "ab";
  container.loadMovie("ab.swf");
 } else if (_root.currMovie != "ab") {
  if (container._currentframe >= container.midframe) {
   _root.currMovie = "ab";
   container.play();
  }
 }
}

this action is applied on a button in the main time line and works well
it didn’t work when i put this btn inside a movie clip

i think the error is in the location of the container

i tried _root , this._parent

actually i don’t understand the difference between them

hope you help me to fix this

Thanks