AS3 hero enemy hittest problem

Hi,
I have been used AS2 up to now. But I need learn AS3 what I can do in AS2.
I try to make a simple game as shown in attachment. I prepare two mc and they are in library. The main stage is empty. First one is hero. The other is enemy. When game is starting hero and 3 enemy movie clips is goingto load to the stage. Enemies have a class as “enemy.as” and they are moving randomly. Hero can be controlled with mouse. I nee the get any action when the enemy mc hits the hero mc. I read messages. But I get 1046 errors. I spent too much time. At the end I accept my fail. To learn the true solution I am writing now here. Please help me.
Thanks already.

Hye ekeneo, do post your codes as well if you need help with it. It’s difficult to know what’s wrong based on your description alone.