Adding If/else To Existing Function For Js Menu?

modifying an existing function which controls the highlighted states of a multi level js accordion menu. I have had to use javascript due to certain css elements not working in safari browsers.My problem is due to the multi level aspect as when a sub link is clicked, the parent link above it then deselects. I need the parent link to stay active when its sub links are clicked and only deselects when a link outside of that list is clicked upon.I understand the theory of adding a conditional statement but simply don't know how to apply it correctly within the functionHere is the existing function which tells a link to be active or selected:var Lst;

function CngClass(obj){
if (Lst) Lst.className='.topnav';
obj.className='selected';

[code]....