Replace the Register button using plugin

[gothicuser]

I am trying to replace the Register button using the plugin system with the traditional 'str_replace'
e.g.

PHP Code:

if ($vbulletin->options['logreg_active'])
{
$find = '<a href=\"register.php$session[sessionurl_q]\" rel=\"nofollow\">';
$replace = '<a href=\"#\" rel=\"#sheet\" id=\"see\">Log In/Register</a>';
            $vbulletin->templatecache['navbar'] = str_replace($find, $replace, $vbulletin->templatecache['navbar']); 


This doesn't work, I gather it's tripping up on the '$session[sessionurl_q]'.

I have tried many variations, but have now got a severe headache!!

Any help or advice would be really appreciated.