Move point object in Screen Reference Coordinate System to picked point on image

(I asked this question on CGTalk but I write here as well, to reach more possible answers for those who only hang here ;)

These premises apply

* I have a background image, set to Aspect ratio is Match Rendering Output
* I have a point object which I want to move in XY in Screen Reference Coordinate System
* I have a point in an image that I use as reference.

We need to establish a relation between the screen width/height and image width/height. Then I need to move the point object to what corresponds with an XY location on that reference image.
I dont know if there is any way to use the image picker in 3dsMax or if I need to type in a value manually that I got from Photoshop.

Any clue how this can be solved?