Terms and conditions on private file download

Hi,

I have downloads that require authorized users to accept terms & conditions before downloading. At the moment this is controlled via javascript, users must check box before download button appears. However all an authorized user has to do to bypass this is right click on the button when it appears/is enabled and copy the link.

I've tried various solutions, 406-mixing-private-and-public-downloads-in-drupal-6, private upload and private download. All seem to lack the one thing I need, prevent users from accessing the location directly by copying the link, thus bypassing the terms and conditions.

Is there a way to enforce this? Do I need to start thinking about obfuscating the link? A few good guesses could be the undoing of that solution.

Any ideas. Please.