Where would the user be when pressing these buttons? On a scene selection menu? While playing the video?
By default (and I believe this to be true with any DVD), the numeric butons correspond to menu buttons in the order that they appear. The first menu button is 1, second is 2, and so on. Just order them the way you want in the project overview window. If you want this to be obvious to the user, though, I'd recommend you number the scenes on the screen (even if the order is obvious -- it might not occur to the user to use numeric buttons).
If you mean that, while playing the video, you want to jump directly to a scene, then No, I don't believe there's a "one button" solution. Most DVD player remotes, however, have some kind of navigation menu that you can "pop up" while watching the video and enter a chapter number. But you don't have to do anything special to put this feature in -- it's part of the DVD specs.