for the undefined thing when you create your own HeathMeter, i got mine to work by creating a new .as file saved it as HealthMeter.as with this code in it
package{
import flash.display.*;
public class HealthMeter extends MovieClip{
}
}
and no more errors with the custom made HealthMeter.
also the bar on the inside needs to have the instance name bar in the properties as in this screenshot
http://i180.photobucket.com/albums/x64/shadowrider189/flashhelp.jpg
 "Shootorial #6: ActionScript 3"){kind=icon}