Password protect downloadable graphics

<A HREF="##FILESAVEPROMPT('sv1','sv2','Save Image','{win}','picture.jpg')##IF({sv1})##FILECOPY('sv3','{ebook}\picture.jpg','{sv2}')##ENDIF"><IMG SRC="thumbnail.jpg"></A>

Now, I would like to add in password protection into the script so that:

1. If the password has been entered and the ebook unlocked, the routine for saveas proceeds as above.
2. If the password has not been entered, the saveas becomes unsuccessful and a dialogue box appears that prompts the user to pay for the password first.
3. At the same time, the images of padlock will change to blank images when the ebook has been unlocked.
4. Some of the images can be saveas to serve as samples, while others will be password protected in order for me to sell the passwords.

4 - I would assume you just leave the code as is

1+2. You'll need to make a script file to save the image

In HREF=

"#!save_picture.as"

Then save_picture.as would contain something like

IF({iscorrectpassword})
MESSAGEBOX('You need to buy a password before you can save!')
ELSE

FILESAVEPROMPT('sv1','sv2','Save Image','{win}','picture.jpg')

IF({sv1})
FILECOPY('sv3','{ebook}\picture.jpg','{sv2}')
ENDIF

I have put up the code as suggested.