Change framerate mode during runtime

Is it possible to change framerate mode during time? If not, is it a limitation of DirectX or would it be possible to implement? As I'd like there to be various video settings in the game.

For instance, myself and many other gamers prefer to play games without v-sync on due to the few frames of input lag (which is essential to get as low as possible for action/reflex based games). I'd rather do the fixed or unlimited framerate option.

There's "Set fixed FPS rate" system action, but looks like there's no way to switch between v-sync and Fixed modes.

Why is there no way to switch? Is it impossible to implement?

Is it possible to add the ability to turn v-sync on or off during runtime?

I'd like players to have the option between screen tearing or input delay.

bump

There is a way of changing the vsync mode to off and on during runtime.You could create 2 exe's of the same game.One has vsync enabled and the other one has vsync disabled.Then you could use the file object to load the unlimited frames exe when the user clicks on vsync off and vice versa.

Yeah thats possible, but it would be good if you didn't have to double the size by having 2 exes.