ActionScript 3 - Add and remove child from stage -

i learning actionscript 3, probaly eazy question pro's. created movie clips want add stage (from library) use of buttons. have total of 6 buttons (and 6 moviclips) trying first 2 work before move on next buttons. problem can't seem remove movie clip when button clicked, or same button... said new @ , think created mess of things... getting error 2007 now

import flash.events.mouseevent; import flash.display.movieclip;  mix_btn.addeventlistener(mouseevent.click, addbear); function addbear(event:mouseevent):void {     var movieclip:bear1 = new bear1();     addchild(movieclip);     movieclip.x = 240;     movieclip.y = 45;   mix_btn.removeeventlistener(mouseevent.click, addbear); mix_btn.addeventlistener(mouseevent.click, removebear); } function removebear(event:mouseevent):void {     var movieclip:bear1 = null;     removechild(movieclip);     mix_btn.removeeventlistener(mouseevent.click, removebear); /*  mix_btn.addeventlistener(mouseevent.click, addbear);*/ } shake_btn.addeventlistener(mouseevent.click, addbear3); function addbear3(event:mouseevent):void {     var movieclip:bear3 = new bear3();     addchild(movieclip);     movieclip.x = 240;     movieclip.y = 45;      shake_btn.removeeventlistener(mouseevent.click, addbear3);     shake_btn.addeventlistener(mouseevent.click, removebear3); } function removebear3(event:mouseevent):void {     var movieclip:bear3 = null;     removechild(movieclip);     shake_btn.removeeventlistener(mouseevent.click, removebear3);     shake_btn.addeventlistener(mouseevent.click, addbear3); } 

var movieclip:bear1 = null; removechild(movieclip); mix_btn.removeeventlistener(mouseevent.click, removebear); 

this part here, try remove null object, it's bad:). applies "snake" , other buttons or movieclips well. if want remove bear you've clicked, try this:

var movieclip:bear1 = bear1(event.currenttarget); removechild(movieclip); mix_btn.removeeventlistener(mouseevent.click, removebear);