Play moviclip using button(as3)

hii, i am new to as3, and trying to develop a small game. i want play a movieclip when i 'll click on button which is placed over another movieclip. The tree structure for this is:

              (in flash layer wise representation ):

             layer1:1st movieclip
             layer2:Button 
             layer3:2ndmovieclip  

according to this representation when i 'll click on 1st movieclip (using button which is placed over that layer ),2nd moviclip will play. and that 2nd movieclip will play once and stop.And this shoud be done whenever i’ll click on 1st movieclip(i.e on button).

So anybody knows the simplest way do it, plz tel me…

if i’m unable to explain my problem then also tel me.