Trouble with getting a session value to work

I have tried on numerous occasions to use a session variable via Server Behaviours --> WebAssist --> Cookies --> Set Session Value and applying these settings of Trigger: Recordset is not empty, Session Name: threadID, Value: fld_fID which is the unique ID I am trying to use.

When I place the session variable 'threadID' on my detail page in design view to test it's working, nothing is displayed which implies it is empty. Why is this?

I watched some of your tutorials on building particular parts of websites, and I seem to have applied similar processes when setting a session variable, but I am not getting a value! I can get the value to display if I place the binding from the recordset, but this isn't going to help in what I need. I am trying to take the unique ID of an article on the detail page and allow users to post a response to it via an insert page. It's the insert page page that needs the unique ID of the original article.

I can do this by using a URL variable, but this isn't particularly brilliant because all a user needs to do is change the ID in the address bar and they could be replying to any other record... so I was hoping to use a session variable.

Basically, I am trying to create a very simple forum!