I think it would be impossible to calculate the depth of the click on a 2D computer screen. If what you want is the z or depth value, why not change the view to front, left, etc. and have the user click on this view to get the depth.
Yes, it is possible with a plug-in object to update a record attached to the object and subsequently update a schedule. Unfortunately, the only way to accomplish this is by programming the plug-in to do the extra work.