prova così
codice:
mio_mc.stop();
function forward(mc:MovieClip)
{
	mc.onEnterFrame = function()
	{
		this.nextFrame();
		this._currentframe == this._totalframes ? this.onEnterFrame=null : null;
	};
}
function rewind(mc:MovieClip)
{
	mc.onEnterFrame = function()
	{
		this.prevFrame();
		this._currentframe == 1 ? this.onEnterFrame=null : null;
	};
}

mioPulsante.onRollOver = function()
{
	forward(mio_mc);
};
mioPulsante.onRollOut = function()
{
	rewind(mio_mc);
};
oppure

// in un movieclip
codice:
onClipEvent (enterFrame) { 
if (_root.rev) { 
frame = this._currentFrame 
frame-- 
if (frame>0) { 
this.gotoAndStop(frame) 
} 
} 
}
// in un bottone
codice:
on (release) { 
rev = true 
}