you could have an image of a tree on a layer above the guy. when the guy walks behind it, it becomes visable, blocking the view of him. when he walks in front, the tree becomes invisable to show the image of the tree on the layer below.
like in the tree's actions there would be something like:
onClipEvent(enterFrame) {
if(_root.guy._y <= #) {
this.visable = true;
} else if(_root.guy._y > #) {
this.visable = false;
}
}
i havent tried it. someone could give it a go