Ajax region selector for oscommerce

Hi all, The project consists in making an ajax region selector for a holiday listing website based on Oscommerce. The user will choose a region for his/her property to list by clicking firstly on a continent, then country and finally on a region within that country. All must be done using ajax to avoid too many page refreshes and to look more user friendly. Continent, country and region are stored as categories in mysql db following the Oscommerce structure. Clipart style image maps are required. Website is already up and running, just in need of this bit.