How to touch anywhere in the screen and the point touched should alwaysstart from a particular point

Am creating a slingshot game in which the object/player will be moving up and down. The user can click anywhere in this part of screen [if(Input.GetTouch(0).position.x< Screen.width/3)] and always the touch should start from the game object position. Since the game object will be moving up and down am not sure how to do this. I have pasted the code below so far what I have done.

{

	private Vector3 slinngshotMiddleVector;
	
	public Transform leftSlingshotOrigin;
	public Transform RightSlingshotOrigin;
	
	public GameObject FruitPrefab;	

	public Transform fruitWaitPosition;


	void Start()
	{
		slinngshotMiddleVector = new Vector3((leftSlingshotOrigin.position.x+ RightSlingshotOrigin.position.x)/2,(leftSlingshotOrigin.position.y+RightSlingshotOrigin.position.y)/2,0);
		initializeFruit();
	}



	void Update()
	{

		if(Input.touchCount>0)
		{
			if(Input.GetTouch(0).position.x< Screen.width/3)
			{
				if (Input.touchCount > 0 && Input.GetTouch (0).phase == TouchPhase.Moved) 
		        {	

                 


				Vector3 currentTouchPosition = Camera.main.ScreenToWorldPoint(Input.GetTouch(0).position);                
				currentTouchPosition.z=0;
                		
				if (Vector3.Distance(currentTouchPosition,slinngshotMiddleVector)> 0.3f && currentTouchPosition.x < slinngshotMiddleVector.x)
				{
						var maxPos = (currentTouchPosition - slinngshotMiddleVector).normalized * 0.3f + slinngshotMiddleVector;			    
					    FruitPrefab.transform.position = maxPos;			                  
				}
				
				else
				{
						FruitPrefab.transform.position = currentTouchPosition;				   
			    }

			    float distance = Vector3.Distance(slinngshotMiddleVector,FruitPrefab.transform.position);

			    }

			}

		}

		else
		{
			float distance = Vector3.Distance(slinngshotMiddleVector, FruitPrefab.transform.position);	
			if(distance > 0.2f)
			{
				Vector3 velocity = FruitPrefab.transform.position - slinngshotMiddleVector;
				FruitPrefab.GetComponent<Rigidbody2D>().velocity = new Vector2(velocity.x, velocity.y) *2.0f* distance; 
				Debug.Log("Thrown Bird");
			}
		}
			
	}


	private void initializeFruit()
	{
		FruitPrefab.transform.position = fruitWaitPosition.position;
	}


		
	
}

@kevinspawner, I did’t understand you question properly but if you want to make your touchable area move with your object than You can use collider in trigger mode and use raycast to detect touch.

Edited:

Here is a package I make for you.
I never make single shot game. I just move platform up down and drag and hold gameObject. as per I understand.
And Code is for single touch.

Steps to import unitypackage.

  1. download package form Here.

  2. create new project.

  3. import package by double click OR from Assets → import Package → custom Package.

  4. And open scene and build and test it.

Let me know it is what you want.(It is not throw gameObject like angry bird. you need to implement by yourself.)