Hmmm, tried but no dice... here is an illustration if I haven't explained it well..

In the front view, I want to slide point A of the red curve (end point), straight down until it snaps to the other curve at point B (where there is NO vertex point)..

tried what you said and it never snaps at all, I'm just dragging it up and down but it never seems to "stick."

Thanks for the quick reply though..