Changing focus point of camera relative to mouse and player

Hi, I got a top down 3D game, similar to angry bots as im sure you all know what that is, and what I would like to implement in my camera is so that it moves when the mouse is moved around the player.

So I would like to move the camera ( offset the camera of the players origin ) smoothly towards the mouse position but clamp it ofcourse at a certain distance so the player is still visible. Same as it is done in angry bots. However Im lost a bit atm, and would really like some help on this.

Thanks in advance