var tree = document.getElementById("tree");
var treeWrapper = document.getElementById("treeWrapper");
var treePusher = document.getElementById("treePusher");

if(treeWrapper!=null && treePusher!=null){

	//get vertical position
	var parent = tree;
	var treePositionY = 0;
	while(parent){
		treePositionY += parent.offsetTop;
		parent = parent.offsetParent;
	}


	//get current wrapper position
	var parent = treeWrapper;
	var treeWrapperPositionY = 0;
	while(parent){
		treeWrapperPositionY += parent.offsetTop;
		parent = parent.offsetParent;
	}

	var height = treePositionY - treeWrapperPositionY;
	treePusher.style.height = height.toString()+"px";
}