Using different themes within same install?

Hi there,

I am looking for a way that will allow me to add additional pages to my blog, but using a different theme, only for these additional pages.

I have seen a plugin that contains it’s own individual theme and adds that theme in as a template, so you can select it when adding a new page. Then that page will have a different theme to the rest of the site.

The only problem is I want to use my own themes for this, not the theme offered with the plugin.

Does anyone know of a way of editing a theme so it can be installed in this way?

Or even know another way of doing it? I’m not all that experienced with wordpress so I don’t know if there’s something else I should be looking for.

Any help would be greatly appreciated