Problem with xml

Hi i’m a newbie here and i’m learning XML with flash and i get to some questions. i put the questions in orange.

i hope that someone could give me a hand for a better xml flash understanding.

best regards
and thank in advance
David
[color=DarkOrange]
//let’s say i have 30 images and i want 5 rows of 6, how can i restrict that.[/color]

thmb_btn.onPress = function() {
myPhoto2 = new XML();
myPhoto2.ignoreWhite = 1;
myPhoto2.load(“graphics.xml”);
myPhoto2.onLoad = success;
function success() {
numimages = myPhoto2.firstChild.childNodes.length;
spacing = 30;
for (i=0; i<numimages; i++) {
picHolder = myPhoto2.firstChild.childNodes*;
thumbHolder = thumbnails.createEmptyMovieClip(“thumbnail”+i, i);
thumbHolder._x = i*spacing;
thumbHolder.nombre = picHolder.attributes.name;
thumbHolder.images = picHolder.attributes.images;
thumbHolder.createEmptyMovieClip(“thumbnail_image”+i, i);
thumbLoader.loadMovie(picHolder.attributes.thmb);
thumbHolder.onRelease = function() {
[color=DarkOrange] this.thumbnails.thumbnail._alpha = 20;
// how can i make the alpha when the thumbnail it’s clicked, because if i use [/color][color=DarkOrange]thumbnails.thumbnail1._alpha = 20; it works but it’s predeterminated and i need it dynamical.[/color]
loader._alpha = 0;
marco._alpha = 0;
loader.loadMovie(this.images);

         };
     }
 }