Selecting columns on a stacked column chart

HTML

<script type="text/javascript" src="http://www.amcharts.com/lib/3/amcharts.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/serial.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/themes/none.js"></script>
<div id="chartdiv"></div>
<div id="debug">Click column secitons to display information</div>

CSS

body {
    font-family: Verdana;
    font-size: 12px;
}
#chartdiv {
	width		: 100%;
	height		: 400px;
	font-size	: 11px;
}
#debug {
    border: 1px solid #ccc;
    padding: 10px;
    margin: 20px;
}

JavaScript

var chart = AmCharts.makeChart("chartdiv", {
    "type": "serial",
    "theme": "none",
    "legend": {
        "autoMargins": false,
        "borderAlpha": 0.2,
        "equalWidths": false,
        "horizontalGap": 10,
        "markerSize": 10,
        "useGraphSettings": true,
        "valueAlign": "left",
        "valueWidth": 0
    },
    "dataProvider": [{
        "year": "2003",
        "europe": 2.5,
        "namerica": 2.5,
        "asia": 2.1,
        "lamerica": 0.3,
        "meast": 0.2,
        "africa": 0.1
    }, {
        "year": "2004",
        "europe": 2.6,
        "namerica": 2.7,
        "asia": 2.2,
        "lamerica": 0.3,
        "meast": 0.3,
        "africa": 0.1
    }, {
        "year": "2005",
        "europe": 2.8,
        "namerica": 2.9,
        "asia": 1,
        "lamerica": 0.3,
        "meast": 0.3,
        "africa": 0.1
    }],
    "valueAxes": [{
        "stackType": "100%",
        "axisAlpha": 0,
        "gridAlpha": 0,
        "labelsEnabled": false,
        "position": "left"
    }],
    "graphs": [{
        "balloonText": "[[title]], [[category]]<br><span style='font-size:14px;'><b>[[value]]</b> ([[percents]]%)</span>",
        "fillAlphas": 0.5,
        "fontSize": 11,
        "labelText": "[[percents]]%",
        "lineAlpha": 0.5,
        "title": "Europe",
        "type": "column",
        "valueField": "europe",
        "alphaField": "europe_fill",
        "showHandOnHover": true
    }, {
        "balloonText": "[[title]], [[category]]<br><span style='font-size:14px;'><b>[[value]]</b> ([[percents]]%)</span>",
        "fillAlphas": 0.5,
        "fontSize": 11,
        "labelText": "[[percents]]%",
        "lineAlpha": 0.5,
        "title": "North America",
        "type": "column",
        "valueField": "namerica",
        "alphaField": "namerica_fill",
        "showHandOnHover": true
    }, {
        "balloonText": "[[title]], [[category]]<br><span style='font-size:14px;'><b>[[value]]</b> ([[percents]]%)</span>",
     ...