How to insert custom template into vB 4.1 template

[SiteTalkZone]

Fixed:
In plug-in, I added following code:

$testVarName = 'testValue';
$templater = vB_Template::create('mycustomtemplate');
    $templater->register('testVarName', $testVarName);
$customtemplate = $templater->render();
vB_Template::preRegister('MEMBERINFO', array('mycustomtemplate' => $customtemplate));