Confusing mask loader

im trying to make a load bar that uses a mask…

basically instead of the load bar going right or left it goes up… and as it goes up it fills in this specific picture… so… anyone know of an easy way to do this… i have a decent but not proficient grasp of AS but i still cant figure out how to get it to load upwards and i still for some reason cant get the mask to work properly …

any help would be appreciated… :slight_smile: tanx