More than one permalink structure?

I’m looking to have more than one permalink structure, 2 exactly and I’m looking for a little direction on how to approach/execute this.

It’s rather simple, I want pages to follow one syntax (www.site.com/%postname%/, and anything in the category ‘Blog’ or even any category to have a separate structure (www.site.com/blog/%year%/%month%/%postname%/). I see the “Optional” settings at the bottom of the Permalinks Settings admin page, but I’m not sure if what I need can be done with the “Category Base” field or if I need to get dirty in whatever (php,htaccess?) can best handle the rewriting tweeks.