Forums / Cotonti / Extensions / Support / Add mCaptcha to contactus plugin

I am trying to add mcaptcha to the contactus plugin which was originally made for seditio but works without problems in Cotonti as well.

I have added the following to the contactus.php:

// Add mcaptcha to contactus
$t->assign(array(   'CONTACTUS_MCAPTCHA' => mcaptcha_generate(),
		  'CONTACTUS_VERIFY' => '<input type="text" name="rverify" size="4" />',));

$rverify = sed_import('rverify', 'P', 'INT');
if(!sed_captcha_validate($rverify))
	{   
		$error_string .= $L['captcha_wrong'].'<br />';
	}

Than I tried to add it to the form itself but that is where I am stuck (yes, I know, I am a php noob )

// adding captcha
$plugin_body .= "<tr><td>".$L['plu_contactcaptcha'].": </td><td>\n;
$plugin_body .= "{CONTACTUS_MCAPTCHA}\n";
$plugin_body .= "<tr><td>".$L['plu_contactcaptcha'].": </td><td>\n;
$plugin_body .= "{CONTACTUS_VERIFY}\n";

// end captcha

I realise it wont work with the tags now in php so I tried to copy how the forum was build with other parts of the contactus plugins, changing it to the mcaptcha variables etc but I keep just getting php errors when I try to acces the contactus page.
If someone can help me on this that would be appreciated