How to create an additional box?

[mailnov]

I am interested to allow my users to not only see the calendar on the browser but also get access to the ics file so they can subscribe from their calendar applications as well. It could be similar like the link to RSS feeds. I would like to provide a subscribe box like the previous/next month, properties, etc. The subscribe box should provide ical and RSS feeds to the different calendars available as well as a hard link to a how-to, explaining how to use it with iCal, iPhone, Sunbird, etc.

How is this best achieved?