is inline use in page node possible without creating a module

Is there a way to write the necessary functions in PHP directly into a Page Node and have it work without having to create a module?

I have a working form already in place using the Form API, I just want to add the activeselect elements and necessary functions along with the rest of the PHP stuff.

Or is the activeselect module specifically designed to be used BY modules, a "standalone" feature (if not available) would be really great here.