restrict Lerp to only one axis?

good morning; when i try to compile this in VS:

 transform.localScale.x = Vector3.Lerp(posA, inputPosB, fracJourney);

it gives me error cs1612, basically what i need to do is scaling an object along an axis non istantly. I also need to translate it to make it look still (bc there is no shear in unity). this is the rest of the script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Lerper : MonoBehaviour
 {
 
     [SerializeField] Vector3 inputPosB = Vector3.zero;
     [SerializeField] Vector3 result;
     [SerializeField] Vector3 avoidBehindCamera;
     private GameObject thisCube;
     private float lengthC;
     [SerializeField] float growFactor = 10f;
     bool isCoroutineRunning = false;
     bool noPosB = true;
 
 
 
     // Use this for initialization
     void Start()
     {
 
     }
 
     // Update is called once per frame
     void Update()
     {
         PosB();
         noPosB = false;
     }
     void PosB()
     {
         if (Input.GetMouseButtonUp(0))
             if (isCoroutineRunning == false)
             {
                 inputPosB = Camera.main.ScreenToWorldPoint(Input.mousePosition + avoidBehindCamera);
 
 
 
                 Vector3 posA = this.transform.position;
 
                 Vector3 journey = (inputPosB - posA);
                 float journeyLength = Vector3.Magnitude(journey);
                 float journeyAngle = Vector3.Angle(journey, Vector3.right);
                 if (transform.position.y > inputPosB.y) { journeyAngle = 0 - journeyAngle; }
 
 
                 Debug.Log(" : inputPosB" + inputPosB + " : journeyLength " + journeyLength + " :  journeyAngle " + journeyAngle);
                 float startTime = Time.time;
                     StartCoroutine(Scale(startTime,journeyLength,posA,inputPosB));
 
                          }
                      }
 
                  private IEnumerator Scale(float startTime,float journeyLength,Vector3 posA,Vector3 inputPosB)
                      {        
                                 isCoroutineRunning = true;
                                 Debug.Log(isCoroutineRunning);
                                 Debug.Log(journeyLength);
                                 Debug.Log(transform.localScale.x); 
 
                 while (journeyLength > transform.localScale.x )
                 {
                     float distCovered = (Time.time - startTime) * growFactor;
                   //  Debug.Log(distCovered);
                     float fracJourney = distCovered / journeyLength;
                     transform.localScale.x = Vector3.Lerp(posA, inputPosB, fracJourney);
             Debug.Log(transform.localScale.x);
                    yield return null;
                 }
                     
                     isCoroutineRunning = false;
                     Debug.Log(isCoroutineRunning);
             }
 
     }
 
 
 if restricting lerp is not possible, is there a better way to do  this?