Need a small Flash Help

I have a flash template which already have a sound in it. It has a button of play and pause. When I export swf file, the sound only plays if I click the play button. For this track its working fine. Now when I replace the sound file, the file does not work this way. I need some one who can teach me how to replace the existing file while keeping every thing else the same as it is. You dont have to do any thing. Just analyze the file and tell me how to do it. Need it in next 2 hours.