random movement

hey, Im new at flash, but Im learn as2 :P
so my problem is that I want to spawn a ball to the middle of the screen, and want it to move with constant speed in random direction everytime its spawned. it sounds really easy, but I cant make it work...
current code Im using for the ball movement is

Code:

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function setBehavior(Ball:MovieClip):Void
{
        var randomAction = random(2);
        switch (randomAction) {
        case 0 :
Ball.xSpeed = Math.random(Ball.mySpeed)*Ball.mySpeed;
                break;
        case 1 :
                Ball.xSpeed = -(Math.random(Ball.mySpeed))*Ball.mySpeed;
                break;
        default :
                break;
        }
       
        var randomAction = random(2);
       
        switch (randomAction) {
        case 0 :
                Ball.ySpeed = Math.random(Ball.mySpeed)*Ball.mySpeed;
                break;
        case 1 :
                Ball.ySpeed = -(Math.random(Ball.mySpeed))*Ball.mySpeed;       
                break;
        default :

                break;
        }
}

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