Another auto-login question

Hi Everyone.

I've searched around the forums and FAQs but not been able to find a solution to my specific problem. I am running a Joomla website, and Gallery 3 is installed alongside. The web site is accessed solely by registered users because of the sensitive nature of its contents.

What I want is to click on a link to take me to galley using a predefined username and password.If this could be a transparent link then so much the better, but if you can see the un/pw in the URL its no big problem.

I have tried creating a link that looks like this:

<my website>/gallery/login.php?gallerypassword=pass&username=user

Unfortunately, perhaps because of the way Joomla works, it just passes me back to the main web site - gallery does not appear to load at all.

Is there some way I can create an auto-login for a single user that I could call from a Joomla web page?