Actionscript code not working someone please check it

well i am making a game where you shoot planes and my shooting actionscript doesnt seem to work and im not sure why.

onClipEvent (load) {
    moveSpeed = 10;
_root.bullet._visible = false
bulletCounter = 1;
bulletSpeed = 17;
this._x = _root.plane._x;
this._y = _root.plane._y-30;
}
onClipEvent (enterFrame) {
this._y -= bulletSpeed;
if (this._y<=-50) {
this.removeMovieClip();
}
}
if (Key.isDown(Key.SPACE)) {
bulletCounter++;
_root.bullet.duplicateMovieClip("bullet"+bulletCounter, bulletCounter);
_root["bullet"+bulletCounter]._visible = true;
}

It seems right but when i try it out it says in the out put box Scene=Scene 1, Layer=Layer 1, Frame=1: Line 15: Statement must appear within on/onClipEvent handler
     if (Key.isDown(Key.SPACE)) {

can someone help me

-xrox2