Kirupa XML photogallery - how to exit the MC

Hi. I have successfully implemented this Photo Gallery Using XML and Flash (by kirupa | 2 September 2004) http://www.kirupa.com/developer/mx2004/xml_flash_photogallery2.htm.
What I am trying to do now in my flashmovie is to exit from this gallery keyframe to a previous keyframe visited (same action as Back button in a web browser), using the “next_btn”. My code edit:
[COLOR=“Gray”]
function loadXML(loaded) {
if (loaded) {
xmlNode = this.firstChild;
image = [];
description = [];
total = xmlNode.childNodes.length;
for (i=0; i<total; i++) {
image* = xmlNode.childNodes*.childNodes[0].firstChild.nodeValue;
description* = xmlNode.childNodes*.childNodes[1].firstChild.nodeValue;
}
firstImage();
} else {
content = “file not loaded!”;
}
}
xmlData = new XML();
xmlData.ignoreWhite = true;
xmlData.onLoad = loadXML;
xmlData.load(“data/059swp/059swp.xml”);
/////////////////////////////////////
listen = new Object();
listen.onKeyDown = function() {
if (Key.getCode() == Key.LEFT) {
prevImage();
} else if (Key.getCode() == Key.RIGHT) {
nextImage();
}
};
Key.addListener(listen);
previous_btn.onRelease = function() {
prevImage();
};
next_btn.onRelease = function() {
nextImage();
};
[COLOR=“DarkOrchid”]next_btn.onRelease = function() {
lastImage();
};[/COLOR]
/////////////////////////////////////
p = 0;
this.onEnterFrame = function() {
filesize = picture.getBytesTotal();
loaded = picture.getBytesLoaded();
preloader._visible = true;
if (loaded != filesize) {
preloader.preload_bar._xscale = 100*loaded/filesize;
} else {
preloader._visible = false;
if (picture._alpha<100) {
picture._alpha += 88;
}
}
};
function nextImage() {
if (p<(total-1)) {
p++;
if (loaded == filesize) {
picture._alpha = 0;
picture.loadMovie(image[p], 1);
desc_txt.text = description[p];
picture_num();
}
}
}
function prevImage() {
if (p>0) {
p–;
picture._alpha = 0;
picture.loadMovie(image[p], 1);
desc_txt.text = description[p];
picture_num();
}
}
[COLOR=“DarkOrchid”]function lastImage() {
if (p = (total - 1)) {
gotoAndStop(“backFrame”);
}
}[/COLOR]
function firstImage() {
if (loaded == filesize) {
picture._alpha = 0;
picture.loadMovie(image[0], 1);
desc_txt.text = description[0];
picture_num();
}
}
function picture_num() {
current_pos = p+1;
pos_txt.text = current_pos+" / "+total;
}
[/COLOR]

Probably not correct, absolute beginner in AS2.0, sorry. Please help.