Use stopAllSounds(); or you can use cSound.stop() if you have a sound object instantiated with name cSound. Then you can load another sound from your library by attaching its linkage name. Linkage names can be given to sounds by right clicking the sound in the library and select Properties and click the check box "Export for ActionScript" then pick an ID name (i.e MyIdSound).
var cSound:Sound = new Sound();
If you want to load an external sound use this script
var cExtSound:Sound = new Sound();
cExtSound.loadSound("ExternSound.mp3", false); //Only mp3 is supported
cExtSound.onLoad = Delegate.create(this, onExternSoundLoad);
Hope this helps
That is indeed very helpful and many thanks. I'll give it a go later today
and will let you know!