Can you animate the graduation or the changing black and white in C4D instead? That way you have full control of the nodes in the gradient and they are animateable. (the gradient can be instant, so a hard area of white moving on a black field is still a gradient, just a really short one). You can twirl down the the attributes of each knot on the gradient color bar to see its position and you can position another color in the next position over to get a hard line instead of a gradient.
You can either animate the plane falloff at the same frame as the gradient keyframe or you can tie the two together with expresso.
If you want to stick with a movie you can click the animation tab in texture in the material and change when the movie starts in the animation and where it ends (this is the two range settings)