Code in buttons layer, frame 1

target = 1;



btnPrev.onRelease = function(){

  target -= 10;

  if (target < 1){ 

    target = 1;

  } // end if

  _root.gotoAndPlay(target);

} // end btnPrev



btnNext.onRelease = function(){

  target += 10;

  if (target >= 40){ 

    target = 31;

  } // end if

  trace ("going to frame " + target);

  _root.gotoAndPlay(target);

} // end btnPrev

Code at end of each animation

_root.gotoAndPlay(_root._currentFrame - 9);