var nav_current = -1;

function init_nav() {
	// do something with nav_highlight
	nav_status_on(nav_highlight);
}

function nav_status_on(n) {
	if (n != nav_current && n != -1) {
		$('navbutton'+n).setStyle('background-image','url(/images/nav_but_'+n+'_on.gif)')
	}
	nav_current = n;
}

function nav_status_off(n) {
	if (n != nav_highlight && n != -1) {
		$('navbutton'+n).setStyle('background-image','url(/images/nav_but_'+n+'_off.gif)')
	}
	nav_current = -1;
}