hitTest help

i tried the hitTest thing on a movie clip and on the frame,the one one movie clip work but not on the frame,here are my codes:

for movie clip:

onClipEvent(enterFrame){
if(_root.box.hitTest(_root.circle)){
trace(“hitting”);
}
}

for the Frame:

function hittest(){
if(_root.box.hitTest(_root.circle)){
trace(“hitting”);
}
}
hittest();

any idea?