Stereo Vision hook

Hi, I'm trying to create a hook that will hack into any game written with DirectX 9 and create a stereo vision effect on the z800 3d Visor just like the Nvidia 3D drivers do, but I need this to work with ATI cards too. The effect I want is that of moving the camera position left and right. One idea was to hook into the setMatrix function, but this won't work because we won't know what the name of the camera matrix will be. Plus many games just pass in the view * projection * world matrix which we can't decompose to get just the view matrix. Another idea was to hook the present() function. Here we could get the backbuffer, copy it as a texture onto a quad and move the quad left and right. This doesn't create a stereo effect because the separation needs to get less and less the deeper we are into the scene. We know it is possible to create this effect because that is what the nVidia drivers are doing, but we don't know HOW they are doing it. If anyone has any ideas please let me know. Thanks, Lance