ActionScript 3.0 :: Making A Undo Button With SharedObject?

I created some Combobox and, when you select each item, a Movieclipappears with a different width,height and name.When it's in the scene you can Drag it to the position you wish.I made two button:Undo(), Redo()for the user who wish to make a previous action,in other words,put the Movieclip to its previous place.I try something with some Arrays that capture the different position when Drag is stopped.I place a Shared Object for registring all the previous position but I don't know how to make it work.So,I show you my code.function of the combobox:

Code:
ComboBoxclassic.addEventListener(Event.CHANGE,select);
function select(evt:Event)

[code]......