apply a filter to forums

Hi, i have a minimal problem that cause Maximus bugs...

i have set a forum setting to apply a language for each forum, and the forum needs to be displayed only for users that select that language in their usercp...

i'm not able to fix the place where to cache the forums to filter this setting...

EDIT: i know that it's not complicated, but i don't understand the forumcache...

how the filter have to work - example:

PHP Code:

if ($thisforum[languageid] == $bbuserinfo[languageid])
{
    //DISPLAY THE FORUM
}
else
{
    //DON'T DISPLAY THE FORUM... IF IT'S A CATEGORY, DON'T DISPLAY THE CATEGORY AT ALL
} 


can someone give me a hint on that ?!

forget it, i finally found ...