Moving bones of a model through code

Hi, Lets see if I can explain myself clearly: I have a rig arm with four bones, a root bone which is at the base, a tip bone at the top and two middle bones. What I want to do is to move the middle bones as if they were following the tip bone so if I move the tip bone diagonally to my up and right position of the screen my middle bones will follow in a normal looking way so that my arm looks as is extending diagonally, a and the game is a 2d sidescroller so I don't have to worry about z position. Right now I have the movement in the y axis working somewhat as I want with this code:

 //stores the bone that is going to be pulled by this one
 public GameObject previousBone;
     
 //when true this allows bone movement, this is for testing purposes
 public bool boneMoving = false;
     
 //stores the bonecontroller script from the other bone
 BoneController control;
 
 //diference in distances when the previous bone will start moving
 public float yDif = 1f;
 
 //percentage of the distance the previous bone will move
 public float yDiv = .8f;
 
 void Start ()
 {
   control=previousBone.transform.GetComponent<BoneController>();
 }
 
 void Update ()
     
 {
 
    if(boneMoving)
    {
     if(this.transform.position.y > previousBone.transform.position.y + yDif)
     {
        previousBone.transform.position = new Vector3(this.transform.position.x,this.transform.position.y * yDiv, this.transform.position.z);
     }
     else if(this.transform.position.y < previousBone.transform.position.y + yDif)
     {
        previousBone.transform.position = new Vector3(this.transform.position.x, this.transform.position.y * yDiv, this.transform.position.z);
     }
             
     if(control != null)
     {
        control.boneMoving = true;    
     }
             
     }
     else
     {
     if(control != null)
     {
        control.boneMoving = false;    
     }
             
     }
 }

This is only for vertical movement but I can't seem to figure out diagonal movement any suggestions are more than welcome thanks.