Wll Dimitri.
How do a user navigate from one page to the next? Is that through URL's or form submits?
The parameter vcname comes in the redirect URL from the InstantAP - so you can use that directly like:
{$vname}. If you want to use the SSID - I believe you can use {$site_ssid}.
Now - first how to solve the URL click to navigate part.
In the footer I placed this code to create a link that also takes with it the parameters in the URL:
<p><a href="urltest.php?{$smarty.server.QUERY_STRING}">Next page</a>
</p>
Now - if you navigate by submitting a form I would assume you can add a field that is populated by the value in the $vcname variable.
You could also check if the variable is saved in any other variable. Add this code to the footer of the subpage to see what parameters are there:
{dump var=$params export=html}