Vertical Alignment of Points on Seperate Parallel Planes

[acelove27]

Basically, I have two workplanes which are parallel to each other and offset by a certain distance. As illustrated in the picture below, I'd like to constrain points from each plane to have the same vertical alignment as those from the other plane (horizontal too, I suppose, but the horizontal dimension will be the same anyways).

I'm not sure exactly how to accomplish this with a definitive constraint, so any help would be greatly appreciated.

[JDMather · Accepted solution]

Project Geometry.