_global. help

hi, im using as2 (cs3), and am having trouble with _global.

i have a button and a movieclip
the movieclip has two frames (both with stop(); in the actions)
the first is called “dont_have” and is blank
the second is called “have_screwdriver” and has my screwdriver on it.
in the actions of the movieclip (SD_inventory), it has this code:

onClipEvent (load){
_global.screwdriver = false;
onClipEvent (enterFrame){
if (global.screwdriver = true){
gotoAndStop (“SD_inventory”, “have_screwdriver”);
(any typos are in here only, ive triple checked my code in AS)
the button has:
on (release){
unloadMovie (this);
_global.screwdriver = true;

when i Test Movie, the SD_inventory shows up on the “have” frame, and clicking on the button does nothing.