Hook after all HTML contents are loaded?

[tbworld]

Since the contents are not user supplied add it to the $show array through hook 'global start' or 'global setup complete', if it must be supplied from the $global.php. $show variable is a global template variable that is already registered -- should be used with caution.

  $show['somevar'] = '/somestring_' . substr(md5(rand()), 0, 2) . substr(rand(), 0, 4);

I am not sure how you are using this variable so I cannot say it will work for you this way.