movie in and movie out

Hi everyone! I'm new here. I hope you can understand what i want to say.

I have 2 buttons, and each of them have a movieclip. When I press button 1 a movieclip is played and the same happens with button 2. What I want is a transition effect. When people press button 2, things from button 1 has to live the screen with a transition, I mean, another movieclip.