function getYPos(elem) {
    actual_elem = elem;
     
    var top = actual_elem.offsetTop;
    
    while (actual_elem=actual_elem.offsetParent)
        top += actual_elem.offsetTop;
    return top;
}

function expandBox() {
	var half1 = 0;
	var half2 = 0;
	var left  = 0;
	var right = 0;
	
	if (document.getElementById('boxPosition_half1') != null) {
		half1 = getYPos(document.getElementById('boxPosition_half1'));
	}
	if (document.getElementById('boxPosition_half2') != null) {
		half2 = getYPos(document.getElementById('boxPosition_half2'));
	}
	if (document.getElementById('boxPosition_left') != null) {
		left = getYPos(document.getElementById('boxPosition_left'));
	}
	if (document.getElementById('boxPosition_right') != null) {
		right = getYPos(document.getElementById('boxPosition_right'));
	}
	
	var max_top = 0;
	if (half1 > max_top)
		max_top = half1;
	if (half2 > max_top)
		max_top = half2;
	if (left > max_top)
		max_top = left;
	if (right > max_top)
		max_top = right;
	
	if (document.getElementById('boxPosition_half1') != null) {
		var diff = max_top - half1;
		document.getElementById('boxPosition_half1').style.height = diff + "px";
	}
	if (document.getElementById('boxPosition_half2') != null) {
		var diff = max_top - half2;
		document.getElementById('boxPosition_half2').style.height = diff + "px";
	}
	if (document.getElementById('boxPosition_left') != null) {
		var diff = max_top - left;
		document.getElementById('boxPosition_left').style.height = diff + "px";
	}
	if (document.getElementById('boxPosition_right') != null) {
		var diff = max_top - right;
		document.getElementById('boxPosition_right').style.height = diff + "px";
	}
}