AutoCAD Visual LISP / AutoLISP :: How To Raise Or Lower Z Value At Any Vertex

I am using acad 2010. I have the ability to draw a 3d polyline on the screen with a different xyz value for each vertex using a digitizing puck. I need a lisp routine that will allow me to adjust the z value only (not the x and y values) on any 3d polyline. I just need to raise or lower the z value at any vertex and repeat if nessasary but I don't want to type it in, I want to raise/lower the z using digitizing puck (with z wheel)....example: I draw a 3d polyline which has 9 vertices with different elevations - vertex #6 is 22.6 (too high) in the z value so I need to drop it to 22.4 without typing it in. Vertex #8 is 12.2 (too low) so I need to raise the z to 12.6 without typing it in and using the z wheel on my digitizing puck. Others have tried and but this is a bit complicated and I may have not expressed it correctly.