Flex :: Using Custom Tooltips For Buttons

I'm using the tooltipManager as described [URL]. I want to display a custom tooltip for the buttons of a buttonbar. The buttonbar's declaration is as follow:
<mx:ButtonBar id="topToolbar" height="30" dataProvider="{topToolbarProvider}"
iconField="icon" itemClick="topToolbarHandler(event)"
buttonStyleName="topButtonBarButtonStyle"
toolTipField="tooltip"/>

Until here, everything works fine. I do see the proper text displaying in a tooltip. Then, I created a custom tooltip manager using the tutorial quoted previously:
public class TooltipsManager {
private var _customToolTip:ToolTip;
public function TooltipsManager() {
} public function showToolTipRight(evt:MouseEvent, text:String):void {
var pt:Point = new Point(evt.currentTarget.x, evt.currentTarget.y);
[Code] .....

Now, this is where I start having issues... I'm trying to get to use this custom tooltip, but I don't know how to get the buttonbar to take it into account. I created a function to see when could I call the functions in my TooltipsManager:
public function showTopToolbarTooltip(e:ToolTipEvent):void{
trace('blabla');
}
But it would seem that it's never taken into account. I've put this function in different buttonbar's events: tooltipcreate, tooltipstart, tooltipend but nothing happens. Not a single trace. Where to call the function of my tooltipManager?