Changing/Adding sidebars…

I have a template that is currently 2 columns. What I would like to do is make the home page a static page that uses the existing 2 columns. However, when you actually go to another page I would like to add a 3rd column.

I know HTML and CSS fairly well. I would call myself a beginner when it comes to PHP. My thought is that it should be possible to just set up 2 different functions. One function that creates 2 columns, and another that creates 3 columns.

Is it possible? Can anyone help me out?

Thanks so much!