Just thought I'd share my little hack to create navigation on a group of subpages belonging to the same folder in the main navigation.
Disclaimer: This was done in somewhat of a hurry, and I haven't used jQuery in a long time, so there's likely a more efficient way to code it. If you know or come up with a better way, please do share it!
The way to use this, is simply by creating a folder in the main navigation with pages in it. Then on each page, using the code block, insert a DIV with the ID "pageMenu".
Then add the code below using code injection