Mega Code Archive
To set the value of a ToolTip in ActionScript, use the toolTip property of the component
public function createNewButton(event:MouseEvent):void {
var myButton:Button = new Button();
myButton.label = "Create Another Button";
myButton.toolTip = "Click this new button to create another button.";
myButton.addEventListener(MouseEvent.CLICK, createNewButton);
addElement(myButton);
}