preloader for data from xml

Hi all,
got a problem that's making me pull my hair out!!

frame 1: Loading data from a xml file:
slides_xml = new XML();
slides_xml.onLoad = startSlideShow;
slides_xml.load("gallery.pop.xml.inc.php");
slides_xml.ignoreWhite = true;
function startSlideShow(success) {
if (success == true) {
rootNode = slides_xml.firstChild;
totalSlides = rootNode.childNodes.length;
firstSlideNode = rootNode.firstChild;
currentSlideNode = firstSlideNode;
currentIndex = 1;
updateSlide(firstSlideNode);

}
}

All's sweet, then [still in frame 1]:
function updateSlide(newSlideNode) {
imagePath = newSlideNode.attributes.jpegURL;
loadMovie(imagePath, targetClip);
}

ok, got the jpeg to be loaded into 'targetClip', but how can I do a preloaded for the image?
Have tried:

Frame 1:
iStatus=0;
setProperty("pBar",_xscale,0);

Frame 2:

iBytesTotal = _root.getBytesTotal();
iBytesLoaded = _root.getBytesLoaded();
iBytes = (iBytesLoaded/iBytesTotal)*100;
setProperty("pBar", _xscale, iBytes);
sStatus=iBytes add "%";

Frame 3:
if (iBytes<100) {
gotoAndPlay(2);
} else {
gotoAndPlay(4);
}

All the above does is create a loading bar for the actual movie, NOT the image 'targetClip'.

How do I find out how much of the 'targetClip' has loaded? Doing my head in...
Thanks in advance