ActionScript 3.0 :: Calling Class Functions With EventListeners

i want to be able to call the function keyDowns() from my main file on ENTER_FRAME. However, i can't seem to get the syntax/definitions right. here's the function within class Hero:

ActionScript Code:
public function keyDowns(event:KeyboardEvent){
if (event.keyCode == 65){

[Code]....

then in the main file i create an instance of Hero called turret i want to call turret.keyDowns() every frame. i'm trying to use this, but i get an error message "1120: access of undefined property event."

ActionScript Code:
stage.addEventListener(KeyboardEvent.KEY_DOWN, turret.keyDowns);
turret.keyDowns(event);