Hittest and detecting range

1

Hi,
I am tring to create a shooting game to shoot a moving object from a fixed target(a tower).
I found the following code on internet and tried to modified it as much as I could…
the frst problem is that when hitTest occurs it does not kill and unload the movie…!!!
the second thing I could not figure out how to stop/start firing when enemy is within or out of range which is say 50 pixel…(perhaps ı should use boolean but not sure how)
if anyone out there help me, ı will be thankfull…

thanks in advance.




var bulletNumber:Number;
var bulletOffset:Number;
var bulletSpeed:Number;
var bulletMaxAge:Number;
var reloadSpeed:Number;
var reloadTimer:Number;
var reloadComplete:Boolean = true;
var radians:Number = Math.PI/180;
var radians2:Number = 180/Math.PI;
loadWeapon("Machine Gun");
function loadWeapon(weaponType:String):Void {
    bulletNumber = 1;
    bulletOffset = 10;
    bulletSpeed = 8;
    bulletMaxAge = 1000;
    reloadSpeed = 700;
}
function fireWeapon():Void {
    if (reloadComplete) {
        createBullet();
    }
}
function createBullet():Void {
    for (var i = 0; i<bulletNumber; i++) {
        var tempBullet:MovieClip = _root.attachMovie("bullet", "b"+_root.getNextHighestDepth(), _root.getNextHighestDepth());
        tempBullet._x = weapon_mc._x;
        tempBullet._y = weapon_mc._y;
        var randomNum:Number = random(bulletOffset)-(bulletOffset/2);
        tempBullet.bulletAngle = (weapon_mc._rotation+randomNum)*radians;
        tempBullet.xSpeed = Math.cos(tempBullet.bulletAngle)*bulletSpeed;
        tempBullet.ySpeed = Math.sin(tempBullet.bulletAngle)*bulletSpeed;
        tempBullet.lifeTimer = setInterval(destroyBullet, bulletMaxAge, tempBullet);
        tempBullet.onEnterFrame = function() {
            this._x += this.xSpeed;
            this._y += this.ySpeed;
        };
    }
    startReloading();
}
function startReloading() {
    reloadComplete = false;
    reloadTimer = setInterval(gunReloaded, reloadSpeed);
}
function gunReloaded() {
    clearInterval(reloadTimer);
    reloadComplete = true;
}
function destroyBullet(bullet:MovieClip):Void {
    clearInterval(bullet.lifeTimer);
    bullet.removeMovieClip();
}
function rotateWeapon() {
    weapon_mc._rotation = Math.atan2(_root.hero._y-weapon_mc._y, _root.hero._x-weapon_mc._x)*radians2;
}
_root.onEnterFrame = function() {
    fireWeapon();
    walk();
    rotateWeapon();
    mouseClicked = true;
};
//b1_btn.onRelease = function() {
    //loadWeapon("Machine Gun");
//};
function walk() {
    //*************************
    _root.hero._x += 2;
    if (_root.hero>400) {
        _root.hero = 10;
    }
    if (_root.bullet.hitTest(_root.hero)) {
        unloadMovie(_root.hero);
    }
    //**************************************          
}