Running animations in Flash Pro 2004 slide presentations

I have a feeling someone will say "well, don't use the slide view" but I am a newcomer to Flash and, as I know the VB and Powerpoint paradigms, so it is more comfortable!

I can't make animations on a single slide work, tho' I can make a video run and stop.

Here is an example. I want a short audio track to run each time you move from slide to slide, as an audio cue of the type of slide you moved to.

I craete a slideset, with the base slide and then three others, all nested at the second level in the base slide.

I import two short mp3 audio files (5 secs long) to the library.

I go to the base slide, create a layer, called "audio", and drag the first mp3 to the slide.

I test it and lo, the mp3 runs OK.

I then go to the second slide and drag the second mp3 onto an audio layer in that slide.

When I test the movie both audio tracks start at once and play over each other.

When I move to the second slide nothing happens.

I only want the audio to start when I move to a slide and stop if I move off it... it didn't seem that tricky at first!

Help gratefully received, the points are based on the need to finish the task.