Hi gvour,
I'm afraid this feature should be provided by Piwik directly ... I can't control it using piwik visitor tracking code.
And it seems that Piwik does not provide features regarding relationship between different visitor peculiarities.
Maybe your needs can fit by Joomla! component tracking user activity ... maybe that's could be useful for you (but I have to admin I never tried)
extensions.joomla.org/extensions/adminis.../admin-reports/20711
Thanks for your appreciation and for your contribution,
Best Regards,
Lhacky