User Interface functions

[HappyTauren]

I need a function that moves unit and changes its height (basically, changes x,y,z) in order for it to be on the same spot on the screen all the time. I will use bilboarded planes that face the screen all the time, but I do not know math well enough in order to make a function that could keep interface buttons (that are units) in place. Is anyone willing to help me around this?
It'd be something like this (http://www.wc3c.net/attachment.php?attachmentid=36907&d=1219960228), but much simpler, as I only need the function to move units to correct positions, I can do everything else on my own.

 

[ThisPOT]

I tried and it gets messy unless you have the visibility of the map fully explored at all times (and even then). Without visibility you wont be able to select/click your unit dummy.

Also when you go out of bounds (your camera can go in fog area) it wont be accurate either as the unit cant follow your camera there.

I am sure there are ways to counter that but in reality it's more complicated than it seems as math alone isn't enough to cover the system.