Changing block templates based on context? moving title in body field in template
You mention the word 'context' in the first line of your question. Take a look at the Context module. I just came from this page 

http://www.metachunk.com/blog/context-based-template-suggestions-drupal-7

Edit: elaborating .. here's the context module 
http://drupal.org/project/context
Install it and create a context 'mycontext' for your 3 pages.

Based on this context, provide a template suggestion as mentioned in Topsitemakers' answer. In your themes template.php, it should be something like (not tested)

mytheme_preprocess_block($&amp;vars) {
  $context = context_get();
  if(isset($context['context']['mycontext'])) {
    $vars['theme_hook_suggestions'][] = "block__mycontext";
  }
}


You can do this more generic as described in the post linked above. Now, your block will render using block--mycontext.tpl.php, if it exists, when shown in the 'mycontext' context. 

$2c,
*-pike