Move points on a rectangle according to a fixed given point.

Hey guys,

I have this probably pretty simple problem I got stuck in. The idea is I have a rectangle (or any geometry for the matter) and I need to move one of the corners inside as it gets closer to a given point (sort of an attractor I'm guessing). So, when the "rectangle" is above this given point the corner should be at a certain distance than it is when the rectangle is at, let's say 10 meters away which should be the initial state of the rectangle.

I tried using a vector method but I can't seem to figure a way to finely control the distance and I'm getting something but I would always need to mirror the end result.

I've also attached a sketch that is probably a lot more clear :).

Any nudge in the right direction is highly appreciated, I'm just searching for a more clever idea to implement this correctly :) And I hope I was clear enough.

Thank you for your time!