Contextual Right Click Menu for Mac OSX

I want to make a contextual menu plugin for mac OS X/Snow Leopard. It will add a new menu item called 'Backup' when you right click on a file or folder. If you select it, it will create a copy of the file/folder in this format: [original_filename].[ext].[date].ver[#].bup where the data in the brackets is swapped out with the relative info. If a file already exists with that info, the [#] in ver is updated. So if I were to right click on '[login to view URL]' and make a backup, I would get this: '[login to view URL]' if I clicked on it again, I would get this: '[login to view URL]' This should work for both files and folders. More info on contextual menus can be found here: [login to view URL]