help with template edit through product

[harmor19]

I have a product and in that product I have

PHP Code:

<hookname>global_start</hookname>
            <phpcode><![CDATA[
            
    $vbulletin->templatecache['navbar'] = str_replace('#<!-- / NAVBAR POPUP MENUS -->#', '<!-- / NAVBAR POPUP MENUS -->Testing', $vbulletin->templatecache['navbar']); 

In the navbar template I want it to look for "<!-- / NAVBAR POPUP MENUS -->"
and replace it with "<!-- / NAVBAR POPUP MENUS -->Testing"