Making collapsible Links - I desperately need help. . .

I am working on a website for my office - stricly for internal
inventory-type purposes.
I have weekly Excel Spreadsheets which I incorporate to pages in FrontPage
which are already set up to use.
However, the 'index' page where these items can be clicked needs some work.

I've been instructed to make each link, which expands to show all the weeks
in each month and their respective inventory counts, expandible/collapsible
or however it should be phrased. Basically I need the link to open to
sublinks upon being clicked.

I may not be explaining this perfectly, but if my request is clear to anyone
who's performed this action before, your assistance will be greatly
appreciated.

Thanks in advance - and by the way, this looks like a great group!

AMH