If you update the Building Blocks in the template that houses them, documents created from templates connected tot he Building Block template will automatically pick up the updated building blocks.
Create your Building Blocks n a template and store that template along with the default Word template for Building Blocks (see Greg's web page I previously cited for more on that).
Then, when you create templates, use that BB Template a a source, but wherever you need the BB, use an AUTOTEXT field so that if the BB changes, you just update the field and the field content will update as well. As long as users have access to both the template
and the BB template, it will all be done automatically, no macros!