How Can we rotate the ENDLESS running background?

Question

Below the code have ability to endless background rotation from upward to downward direction OR something else way.

I just want opposite from this rotation. I tried but could solve this problem.

Anybody suggest me , how to do this ?

private void animateBackground() {
    _oddBackground = CCSprite.sprite("sky.png");
    _evenBackground = CCSprite.sprite("sky.png");

    /*from Upward to Downward direction background rotation */

    _oddBackground.setPosition(winSize.width / 2, winSize.height / 2);
    _evenBackground.setPosition(winSize.width / 2, winSize.height + (winSize.height / 2));
    schedule("scroll");

    addChild(_oddBackground).addChild(_evenBackground);
}

public void scroll(float dt) {
    // move them 100*dt pixels down
    _oddBackground.setPosition(_oddBackground.getPosition().x,   _oddBackground.getPosition().y - 100 * dt);
    _evenBackground.setPosition(_evenBackground.getPosition().x, _evenBackground.getPosition().y - 100 * dt);

    // reset position when they are off from view.
    if (_oddBackground.getPosition().y < - winSize.height / 2) {
        _oddBackground.setPosition(winSize.width / 2, winSize.height / 2);
        _evenBackground.setPosition(winSize.width / 2, winSize.height+ (winSize.height / 2));
    }
}