Help, I need Timed Events!

ok i am trying to set up a banner so after a relative amount of time passes, so does the image in display. i dont want to go about the ghetto way with putting sets and sets of empty frames and play it looped.

if thats possible can some one fill me in =].

another thing, i have a external .swf system, but can i make those play in randomly? or should i put everything in one .swf?

help, and thanks in advance.