Including external scripts on blogger blogs?

I'd like to add a shout out box to my blogger.com blog. It's got to be 'proper', I want to avoid using iframes and third party tat :rolleyes: The php shout out scripts would be hosting remotely on my own server, so I need a way to include external files on the blogspot html pages. I've looked through the help documentation, but it doesn't make much sense to me :confused:

Well how much control of the blog do you have? Can you write your own code for it? Can you use php includes?