Loading mcs from a button

on a button (on release) I want a movie clip in the libary to be placed on the _root timeline on frame 140(the button is on 118) and I want to be able to make sure it is placed correctly (x-47.0 and y-19.5). Now on each button(9 of them)a different mc with be placed on the root timeline and I need the prievous mc that was loaded if there was one to be unloaded cause th bg is transparent.

Well I just awnswered part of my question a mc cant be loaded that isnt on the timeline but what I need to do now is fighure how to change the position of the mc.

on (release) {
this._parent.chair_mc._x = -49.1;
this._parent.gotoAndPlay(103); works
but not when I try to call chair_mc
all I want to do is change the position of chair_mc when you click on a button. This aint this hard I dont know why I cant figure it out please help