Step:1 - Make MovieClip at first keyframe in Scene of Flash
Step:2 - Extend timeline of Scene upto hundered frames
Step:3 - Insert Another Layer at main timeline of scene.
Step:4 - Write [First frame] on textbox at First keyframe of second layer.
Step:5 - Write [100th frame] on textbox at Hunderedth frame of second layer
Step:6 - Insert third layer and write [label:-"a"] at hundredth keyframe on timeline.
Step:7 - Make a button inside MovieClip then write the Code on button writen below
on(release){
_parent.gotoAndStop("a");
}

Step:8 - Look the change in screen.

Note:- The above code is valid for flash versions upto Flash player version Eight.