Illiana-
Your example doesn't make any sense (jsfiddle). All you are doing is calling a function on document load to overlay the chart. Can you please work up an example that works with the chart's events. For example this does NOT work:
http://jsfiddle.net/petf7tbb/
dataBound: function(e) {
var showMessage = this.dataSource.data().length == 0;
if (showMessage) onDataBinding();
}