[Tiki-users] Wiki Argument Variables and Plugins

Hi,

Can someone point me to a description of how Wiki Argument Variables
and Plugins interact?
If I put {{itemId}} in a page and add itemId=22 to its url (query
string), I see a 22 substituted into the page. If I put item
{{itemId}} into parameter exactvalue of {trackerlist trackerId="4"
fields="28:32:26:25:24:17" filterfield="23" exactvalue="{{itemId}}"},
I get an empty result set. I do not think the variable substitution
works in this case. It is probably related to how argument variables
and plugins are processed, but I did not find any relevant
documentation.

Thanks,
Ilya