onData jpg

Hi,
I am loading jpg’s, and I want to make a Movieclip(‘MC’) invisible when there is no jpg to load (because it just is not there). How can I detect if there is no jpg, and then make the MC invisible? I think I should use onData, but I can’t make it work.
[AS]
function laadNail3(foto) {
var my_lv:LoadVars = new LoadVars();
my_lv.onData = function(src:String) {
if (src == undefined) {
MC._visible = false;
}
foto = src;
};
my_lv.load(foto, holder);
}[/AS]
I am also confused where to put the Movieclip that holds the jpg (‘holder’)?

The data passed to the function comes from another swf, saying:
laadNail3(“b3.jpg”);[/AS][AS]

Could someone show me how to do this?

thank you,

Jerryj.