[question] using addChild?

I am not having fully knowledge about ObjectDisplay abstract class.

i have a timer class that i instantiate to use in my ‘my menu’ interface to do some action

like when i press button it runs 30 secs then when its done it says ‘done’ in output.

i want timer class to also add an object to the stage… like its a created creature after 30 seconds passes for example. but it seems impossible to use addChild anywhere else but in document class why ? and how can i overcome that ?

if i just try it it gives the following error
C:\Documents and Settings\Pelevet\Desktop\Flash_timer.as, Line 33 1118: Implicit coercion of a value with static type Object to a possibly unrelated type flash.display:DisplayObject.

solutions ?
thanks