Constrain a set of referenced points in grasshopper

How can you constrain a set of grasshopper initialized points to only be movable in the z axis in the rhino viewport. Is there a method to selectively disallow points to be moved in x and y directions or to limit the options available on the gumball for these particular points?

Behavior required; the user moves the point using the gumball handle, if any displacements in the x and y are detected on mouse release the point goes back to prior position (refuses to move).

I don’t know whether there is a way to constraint gumball movement to one or more axes, but a workaround could the to deconstruct your referenced point and use its z-coordinate, as well as its initial x- and y-coordinates for the new points x and y.
When you move your initial point, only the z-value of the new point is going to be updated this way.

This is a valid method, I am actually resorting to this system at the moment. I am looking for somthing more intuitive in the rhino viewport. This should resemble a modified gumball or a custom handle for the point object.