I looked around but couldn't find anything.
You could attach an AppleScript to the external hard drive. This would keep out the non computer savvy but it's possible to remove attached scripts without typing in a password.
If you deiced to do this this is what you do:
Open Script Editor.
Copy and past this code into the Script Editors window.
Code:
on opening folder this_folder
set the_password to "iwantin" --set this to your password you want to use.
set secret_folder to "secret stuff" --set this to a folder inside of your external hard drive. This is where you need to protected files.
tell application "Finder"
activate
close window of this_folder
end tell
set the_prompt to "Please enter your password:"
repeat
tell current application
activate
display dialog the_prompt default answer "" buttons {"Cancel", "OK"} default button 2 with icon 0 with hidden answer
if the text returned of the result is the_password then
exit repeat
else
beep
set the_prompt to "Incorect." & return & "Please enter your password:"
end if
end tell
end repeat
--set this_folder to "FLASH DRIVE"
tell application "Finder"
activate
open folder ((startup disk as string) & "Volumes:" & (the name of this_folder as string) & ":" & secret_folder & ":")
end tell
end opening folder
Edit the line:
set the_password to "iwantin"
Change "iwantin" to you password of choice.
Edit the line:
set secret_folder to "secret stuff"
You have to create a folder inside of your external hard drive and put all you stuff there. This is the only folder you will be able to accesses.
Save it as a script in "
your username/Library/Scripts/Folder Action Scripts" (or anywhere really)
Plug in your external hard drive.
Right click (ctrl click) it and select "Enable Folder Actions". If it's not there then skip this step.
Right click it again and select "Attach a Folder Action
"
You will then be asked to select a scrip to attach. Navigate to where you saved the script above and click "Choose".
Now try and open the external hard drive and see what happens.