animated drop-down menu buttons won't respond onRelease

I created a drop-down menu movie clip. Within it are multiple buttons which change their alpha values. I'm having an impossible time of getting the buttons to respond to an onRelease from the maintimeline.

for instance:

stop();
_root.menu_mc.print_btn.onRelease = function(){
gotoAndStop("print1");
}
_root.menu_mc.illustration_btn.onRelease = function(){
gotoAndStop("illustration1");
}

I can't place any code directly on the buttons because later in the timeline the actionscript needs to change for the same buttons:

stop();
_root.menu_mc.print_btn.onRelease = function(){
gotoAndStop("print2");
}
_root.menu_mc.illustration_btn.onRelease = function(){
gotoAndStop("illustration2");
}