AJAX - Menu item class needed.

I would need an AJAX menu class, consisting of dropdownfields, which should asynchronously send their values onchange to the server and alter a DIV-container. The class should be written, so that it is easy to change the amount of dropdown-fields, as I want to use this menu on different sites. You can get a peek at what I want at [login to view URL] (site is in german, please just look at the droddown menu at upper left side) I will take care about PHP scripting myself, just the menu is needed with documentation, where to add additional formfields or where to remove them.