I believe he wanted a constant linear speed. Here's my take on it, using your formula.
Close but no cigar. But I think I have something to work with. Thanks.
What I'm trying to do is more of a movement system.
1 The red box should always face the Mouse pointer. This is where it is looking.
2 pressing arrow up or down should move the box closer or further from the mouse pointer.
3. Pressing left or right should orbit the red box around the mouse pointer, clockwise or anti-clockwise. Based on the distance to the mouse pointer (this distance is relative)
I think I have what I need from your example to solve the last few bits. Thanks.