Sorry for being annoying need help in movieclip movement

heres the scenario … im creating a presentation where my movieclip to slowly move to direction Left and right while pressing the keyboard with its respective keys (<Left> and <Right>)…
thank you so much for the tutorials…
ive learned how to that… but my problem right now is that i want my movieclip to stop when it reaches a certain position… so it wont continuously run in the direction… i Press…
right now im using this script… compliments from this forum BTW:beam:

onClipEvent(load)
{
acceleration=0;
}
onClipEvent(enterFrame)
{
if (Key.isDown(Key.LEFT))
{
acceleration–;
}
if (Key.isDown(Key.RIGHT))
{
acceleration++;
}
myangle=_rotation;
xmov=Math.cos(Math.PI/180*myangle)acceleration;
ymov=Math.sin(Math.PI/180
myangle)*acceleration;
_x+=xmov;
_y+=ymov;
}

… i could stop my movie clip when if press the other direction… but i was thinking that could it be stopped in a certain position even when pressing the key ive used.

thanks so much for your help Guys:beam: