Flip image

The code below doesn’t work to me because it is flipping the image all the time, and not on it’s center (now it turns from right to left).

this._xscale *= -1;

I want to that the image flips automatically within every 2 seconds on its center. I would be happy if anyone could tell me where I can read about how to make a script that plays the movieclip.
Cardflip is a similar effect that descripes how I want to flip the image. The different is that the cardflip flips the image at onmouseclick, I don’t want any on_mouse, but play();