Using Folder Actions

Folder Actions enables you to attach scripts to Finder folders. When the folder is opened, closed, or modified, the script activates automatically. This makes it possible to automate many organizational tasks.

For example, suppose each time you add a file to a folder, you want that file backed up to another disk location. You can create a script that performs the back up and attach that script to a folder. Then, when a file is added to the folder, the script runs and the file is backed up.