you have your solution in your drawing! :)
 use 3 square sprites(set them invisible of course during runtime ) and place them along your trampoline surface.then say
Player on collision with "left sprite"
and platform is falling                    set platform y -500
                                           set platform x -200
Player on collision with "center sprite"
and platform is falling                    set platform y -500
                                 
Player on collision with "right sprite"
and platform is falling                     set platform y -500
                                            set platform x 200