firing an function on completion of another

Hello all!
quick and easy question, i'm sure:

i would like to fire a function upon the completion of another function, but i'm not sure how. what i want to do is add a TextField to a MovieClip after a tween has occurred on that MovieClip. would some sort of Event.COMPLETE listener be appropriate? can an event listener listen for the completion of a function? if so, how would i go about that? I'd post the code, but there's a bunch of extraneous stuff in there, so i don't want to distract from what I'm sure is a very simple question with a very simple answer. Any help would be greatly appreciated.