Moving players arms and legs via mouse movement?

Hello fellow Unity users

I have been trying to figure out a how to write a C# script so when the player holds down a key ("A" for example), then starts to move their mouse the assigned arm or leg from character will move along with the mouse movement.

I have done a some research on the matter and I believe that I need to assign either a wrist or ankle joint from the character rig and map it to a key on the keyboard. As long as the mapped key is being held down the joint can be influenced by the mouse.

if more info is need I will try my best to explain it in greater detail.

Thanks Rob Lloyd