Button enabled problems

Hello,

I am building a image gallery and i have a prev and next button that need to disable and a close button needs to be enabled when its open. So i have the close button under the next button and am using the following:

function galleriesOpener(){
if (nav._y== 457){
new Tween(nav, "_y", Regular.easeOut, nav._y, 27, 10, false);

nav.thumbnails_btn.enabled = false;
nav.prev_btn.enabled = false;
nav.next_btn.enabled = false;
nav.close_btn.enabled = true;

new Tween(nav.thumbnails_mc, "_alpha", Regular.easeOut, nav.thumbnails_mc._alpha, 0, 10, false);
new Tween(nav.prev_mc, "_alpha", Regular.easeOut, nav.prev_mc._alpha, 0, 10, false);
new Tween(nav.next_mc, "_alpha", Regular.easeOut, nav.next_mc._alpha, 0, 10, false);
new Tween(nav.close_mc, "_alpha", Regular.easeOut, nav.close_mc._alpha, 100, 10, false);
} else if (nav._y== 27) {
new Tween(nav, "_y", Regular.easeOut, nav._y, 457, 10, false);

nav.thumbnails_btn.enabled = true;
nav.prev_btn.enabled = true;
nav.next_btn.enabled = true;
nav.close_btn.enabled = false;

new Tween(nav.thumbnails_mc, "_alpha", Regular.easeOut, nav.thumbnails_mc._alpha, 100, 10, false);
new Tween(nav.prev_mc, "_alpha", Regular.easeOut, nav.prev_mc._alpha, 100, 10, false);
new Tween(nav.next_mc, "_alpha", Regular.easeOut, nav.next_mc._alpha, 100, 10, false);
new Tween(nav.close_mc, "_alpha", Regular.easeOut, nav.close_mc._alpha, 0, 10, false);
}
}

The problem is the disabled button is preventing my rollover to work on the button underneath it, so i am wondering how i can make the next button completely disabled.

thanks