need advise to modify javascript

I located a javascript (by sandeep over the internet and tried to modify to suite my need but unfortunately i need help. Right now the script does not collapse when there is no sub-menu link. For example..

main-menu without submenu

main-menulink1
-submenu-link1
-submenu-link2

main-menulink2
-submenu-link1
-submenu-link2

All collapsed when open..then user click on main-menulink1 it opens the submenu and if the user click on main-menulink2 the main-menulink1 will collapse. But, when the user click on main-menu without submenu the main-menulink2 will not collapse. I WANT ANY main-menulink THAT OPEN TO BE COLLAPSED WHEN THE USER CLICK ON main-menu without submenu.

I TRIED THIS BUT NOT WORKING<div onClick="openClose('MN',mainNum,'a3')" class="main"> <a href="main-manu without_sublink.html">main-manu without sublink</a></div>

<div onClick="openClose('MN',mainNum,'a1')" class="main"> <span class="mainLink">main-menulink1 &nbsp; <span id="tick_a1">+</span></span></div>
<div id="a1" class="sublinks1">

<a href="sublink1.html" class="link">sublink1.html</a><br />
<a href="sublink2.html" class="link">sublink2.html</a><br />

<div onClick="openClose('MN',mainNum,'a2')" class="main"> <span class="mainLink">main-menulink2 &nbsp; <span id="tick_a2">+</span></span></div>
<div id="a2" class="sublinks1">

<a href="sublink1.html" class="link">sublink1.html</a><br />
<a href="sublink2.html" class="link">sublink2.html</a><br />


if (document.getElementById) {
document.writeln('<style type="text/css">')
document.writeln('.main {text-decoration:none; color:black; cursor:hand; cursorointer}')
document.writeln('span:hover.mainLink {text-decoration:underline; color:red}')
document.writeln('.sublinks1 {display:none; padding-left:14px}')
document.writeln('.link2 {text-decoration:none; color:blue}')
document.writeln('a:hover.link2 {text-decoration:underline; color:red}')
document.writeln('</style>') }

// Below you should add a1, a2 etc. for each main link you wish to include
// so if you want 3 main links you should add a1, a2, a3 in the format shown
// enclosed in double quotes
var mainNum = new Array("a1","a2","a3","a4","a5");

// Below you should add b1, b2 etc. for each sub link you wish to include
// under one main link, here the first main link. so if you want 4 sub links you
// should add b1, b2, b3, b4 in the format shown enclosed in double quotes
var subNum1 = new Array("b1","b2","b3","b4","b5","b6","b7","b8","b9");

// Below, this is for sub links under the second main link. there are 3 sub links
// in the given example
var subNum2 = new Array("c1","c2","c3","c4","c5","c6");


function openClose(theName, menuArray, theID) {
for(var i=0; i < menuArray.length; i++) {
if (menuArray == theID) {
if (document.getElementById(theID).style.display == "block") {
document.getElementById(theID).style.display = "none";
document.getElementById("tick_"+menuArray).innerHTML = "+";
eraseCookie(theName); }
else {
document.getElementById(theID).style.display = "block";
document.getElementById("tick_"+menuArray).innerHTML = "-";
newCookie(theName,menuArray,exp); }
}
else {
document.getElementById(menuArray).style.display = "none";
document.getElementById("tick_"+menuArray).innerHTML = "+";
}
}
}

function memStatus() {
var num = readCookie("MN");
if (num) {
document.getElementById(num).style.display = "block";
document.getElementById("tick_"+num).innerHTML = "-"; }
var num1 = readCookie("SB");
if (num1) {
document.getElementById(num1).style.display = "block";
document.getElementById("tick_"+num1).innerHTML = "-"; }
}

// Multiple onload function created by: Simon Willison
// http://simonwillison.net/2004/May/26/addLoadEvent/
function addLoadEvent(func) {
var oldonload = window.onload;
if (typeof window.onload != 'function') {
window.onload = func;
} else {
window.onload = function() {
if (oldonload) {
oldonload();
}
func();
}
}
}

addLoadEvent(function() {
memStatus();
});