How to add a dynamic Folder to the iPhoto Mediathek?

Hi,
i wanted to know, if it is possible to add a Folder with dynamic content to the iPhoto Mediathek?

For example:

- In Folder "xy" at the desktop are many .jpgs-Datas

- Everyone copies some more jpgs from a USB Stick to the folder "xy"

- After a few times, we open iPhoto

- IPhoto checks the Folder "xy" and see that there is content that isn't in the Mediathek, yet.

- IPhoto adds the different content to the iPhoto Mediathek → after that the folder ist up to date with the folder in the iPhoto Mediathek (synced)

Background:
I wanted to add a Dropbox folder with my camera uploaded data to my iPhoto Mediathek.

The content in both (iPhoto & Dropbox Folder) should always been synced.