Randomly Load Movie Clip When Page Loads?

I am trying to make what I thought would be a very simple random picture display. I have five movie clips named myClip1, myClip2, etc. All are on the first frame of the timeline. Each has this as a movie clip action:

Code:

onClipEvent(load){
_alpha = 0;
}

The frame also has an action like this:

Code:

nClipMax = 5;
// nClipMax being the number of movie clips
this["myClip" + Math.ceil(Math.random()*nClipMax)]._alpha = 100;

When I test this the background (an image) displays but nothing else, the movie clips stay transparent. I have tried several variations without any luck.I am mainly an asp and net developer that uses flash periodically so be gentle.