i dont know how the stuff the guys said doesnt work for you. All those ways work, but if you want the easiest, it would be IMO to make a blank movieclip that has blank frames in it except the last frame which says "go to and play" your scene that you want.

If you want approximately 20 sec, and your running your animation at 18 Fps, then just make a movie clip with 360 frames in it (18fps * 20sec). When it reaches frame 360, appx. 20 sec will have elapsed and you can have it send you to the next scene. This would be your timer i guess.

Of course this may be the easyest but also the one with least control. GetTimer is a better solution for exact measurements.

Anyway Gl with it, let us know what happens.