Syntax help with dynamic this.i

I have a photogallery where I’m dynamically loading full-size jpgs and then downsizing them to thumbnails. additionally, I’m creating another empty movie clip on top of each image so I can change the appearance of the images (alpha, blue tint, green tint, etc.)

so all of the thumb mcs are created in a loop and named mc* (mc1, mc2, mc3, mc4 etc.) Then another empty movieclip is created as a child of the mc and named cover* (cover1, cover2, cover3, cover4, etc.). If I debug and look at the objects, they all show up. Here is an example of one;

Movie Clip: Frame=1 Target="_level0.thumbs_mc.mc65"
Movie Clip: Frame=0 Target="_level0.thumbs_mc.mc65.cover65"

So, I have a function that enlarges the image, but when the image gets clicked on, I also want to change the alpha property of the cover movieClip. Right now, I can make it work if I hard code in the cover like this;

setProperty(this.cover0, _alpha, 0);
setProperty(this.cover1, _alpha, 0);
etc. for each cover mc.

what I want it to do is to dynamically pull in the number of the mc that is clicked. Right now, if I trace this.i I get the correct number of the mc that was clicked. I have tried many things such as

setProperty(this.cover*, _alpha, 0);
setProperty(this.cover[this.i], _alpha, 0);
setProperty(this.cover+i, _alpha, 0);

any many more.

This is killing me - can anyone help me with the syntax? I’m guessing it’s something simple that I’m missing.

Thanks in advance.