Make banners appear on specific pages

Hi,

I need a very simple mod: add a field in the Dolphin's admin-> banners page that would define where this banner is being showed.

The field would simply list all the existing Dolphin's pages. It would be cool if multi selection was allowed in that field. See attached (fabricated) screenshot.

I saw in the forum how to make this work if I want to allow the banner on all pages BUT some specific page. However I want to achieve the opposite - show the banner ONLY on a specific page.

Thank you!