Thx a lot Cellarius!
Just a little correction. Code should looks like this:
PHP Code:
$templater = vB_Template::create('pb_latestthreads_area'); // create the template
$templater->register('pblatest_bigblocks', $pblatest_bigblocks); // register $pblatest_bigblocks to be able to use {vb:raw pblatest_bigblocks} in template pb_latestthreads_area
$templatevalues['pb_latestthreads_area'] = $templater->render(); // rendering template into a variable suitable for preregistering for use in existing template
vB_Template::preRegister('FORUMHOME', $templatevalues); // preregister variable from line above to be able to use {vb:raw pb_latestthreads_area} on forumhome