ActionScript 2.0 :: Change Movieclip Buttons State When Timeline Reaches A Certain Frame?

I have a menu with 4 movieclip buttons (movieclips that act as buttons) that when pressed make the timeline jump to a certain frame. The mc buttons have both "onrollover" and "selected" states. However the timeline also moves on its own, even if no button is pressed.

I need the buttons to assume the "selected" state when the timeline reaches a specific frame (as if the button had been pressed to make the timeline jump there). But I can't figure out how to do it althought I think it must be quite simple.

This is the code I'm using (controls the buttons and its on the first frame of the main timeline)

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// create an array of all nav buttons in group
var groupinfo:Array = [birds, bears, bats, bunnies];
// create constants to define start and stop of fadein and fadeout sequences
// (fadeout should be exactly the same sequence as fadein, in reverse frame order)

[Code].....