You can't "force" a game to run on DX11. Games that support DirectX 11 will use its features if they are available on your system, but games that don't support DirectX 11 will still use DirectX 10 or 9 if they are available. There is no way to "trick" a game into using a different version of DirectX. However, you may get some games to run in DirectX 11 mode by modifying the application's .exe file with a hex editor. But note that this is unsupported and may not work with all games.