mp3 buttons

You haven't shown me the code that you're referring to, so its difficult to quess what you're looking at. I would do that operation like this:
1. create one button for each sound that I want to play.
2. create a sound channel object for each sound.
3. import each sound and attach it to a sound channel object.
4. set a variable to hold the value of the current sound, probably its sound object name.
5. set a property for each sound object to hold the position for that sound when it is stopped, if you want a pause feature.
6. attach a mouseUp event handler to each button.
7. have the mouseUp event handler, the function, tell a particular sound to play and the current sound to stop playing and, possibly, store the current position of the just stopped sound so that it will begin at that point when played again.
8. create a volume, and possibly, a pan, control to control the playback volume and pan of the sound.

Here's an example file that does all of this and more: http://schoolofflash.com/2008/03/22/flash-xml-music-player-in-actionscript-3/