JavaScript and Select.Options

I have a form (as a dialog box) that has a ListBox on it with values as computed from 2 hidden fields. Then, i have a button (ADD) which is trying to add an option to it using Javascript. In the onClick event, which is operating in the Notes Client only:

var rlinks = document.forms[0].RelatedLinks;

var index = rlinks.selectedIndex;

rlinks.options[rlinks.options.length]=new Option(‘New Item’,‘New Item$NewURL’);

This doesn’t add a new item. In addition:

rlinks.options[rlinks.options.length-1]=null;

doesn’t delete an item.

Does Javascript not work for field manipulation in the Notes Client? Or is there some setting that needs to be done to make it work.

THanks

Mike