Page direct linking prevention

[crkgb]

I have an external third-party poll script that allows me to let unregistered visitors vote. It tracks votes by IP address and prevents voting from the same IP. The poll page opens up by the onClick method that pops up a window stripped of all toolbars (as much as possible).

The link to a poll is located on my vbAdvanced static page and I want all voters to go through that static page before voting. Therefore, I want to check in my third-party script where people came from and redirect them to that static page if they came from a direct link on some other website. Any suggestions on how to do it?

My first attempt was to use the REFERER passed by a browser, but it turned out that IE does not pass it when a link is opened via onClick method.

Then I tried setting my own cookie with JavaScript bit through the onClick method, but IE did not do it either.

I could probably use the bblastvisit vBulletin cookie value to check if it is set and is it's fairly new, but I cannot figure out how often it gets updated. Doesn't seem to be changed when I visit my site again and again.

Does anyone have any idea on how to determine if a visitor came from my designated page, or some direct link on other site? I know that the above methods (if they worked) are not bullet-proof and skilled users can alter referer and cookie values, but I am not concerned about that small portion of my visitors.

[crkgb]

Anyone?

[crkgb]

Am I the first one in the world trying to do it?