Help loading a movie with button

I want to complete the following:

http://prgn.ernci.com/escalator.swf

The user clicks on a button (1 of the windows) then on release a new mc (it will be some text goingdown the armrail of the stairs) starts to play

However, i have looping animation and sound on in the background so i can’t do a gotoandplay can i?

Please help thanks