Pause fade out

Hi all, I’m putting something together in Flash using AS in place of tweens (so I can learn AS) and I’ve run up against a little problem. I have an image covered with three blocks that I’m fading out using AS so they act as masks. Problem is, I’d like the second to run after a slight delay and the third after that. How can I do that?
Here’s my fade code that’s attached to the instance on-stage.

onClipEvent(enterFrame) {
speed = 2;
this._alpha -= 30;
}