automator for external HD?

Hi,

I want to build a database with files/folders on an external HD.

The HD is all set up and running, and I can add folders/subfolders/etc to it.

However, to protect myself against my own carelessness, I need some kind of a setup, possibly an Automator action, to prevent accidental writing/removing/editing of items on that HD.

I want an action that would demand a password when I try to add/delete/modify a folder/subfolder/item from the external HD.

The password should be demanded each time I try to add/delete/modify regardless of whether the HD has already been mounted. It should apply to all levels of the HD (folders, subfolders, individual items)

However, no password should be required when I read or copy from that HD.

I use a Power Mac and an Intel-based Mac running OS 10.5.8.

Many thanks for any suggestions.