NaN as value of ComboBox results

I want to calculate the sum of the selected value of ComboBox cb1 and cb2.
It seems that the result is a txt variable and not a Number. And that's the problem.
The result must be a 'Number'value and not a textvalue!
I've changed the result value with int(), Number(),.. etc without success...

// create 3 combobox with the names: cb1, cb2
 
var cb_1_count:Number=0;
var cb_2_count:Number=0;
var total:Number=0;
 
for (var i:Number=1; i<=5; i++){cb1.addItem({data:[i], label:[i]});}
for (var i:Number=1; i<=3; i++){cb2.addItem({data:[i], label:[i]});}
					
var cb1Listener:Object = cb1;
cb1Listener.change = function(event_obj:Object) {
	cb_1_count = (event_obj.target.selectedItem.data);
	calculateIt();}
cb1.addEventListener("change", cb1Listener);
 
var cb2Listener:Object = cb2;
cb2Listener.change = function(event_obj:Object) {
	cb_2_count = (event_obj.target.selectedItem.data);
	calculateIt();}
cb2.addEventListener("change", cb2Listener);
 
function calculateIt() {
	total = Number(cb_1_count) + Number(cb_2_count)
	trace (total); // MUST BE NUMERIC!
	}

Select allOpen in new window