Rube Goldberg Machine HELP!! ASAP?

ok so we are trying to turn on a radio so so far we are working backwards so we have a bouncey ball in front of the cd player then books are stacked in front of the ball like a domino effect in in front of a book is a tricyles and in front of that is a computer rolly chair once we push the chair it all triggers making the music play but we are now stuck as to what can make the computer chair move forwad and so on please help.!!!