ease in and out between blendshapes

Just trying to ease between 2 blendshapes. Read docs but cant get it working. Any help would be appreciated

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class lerpTest : MonoBehaviour {
 
 
     private SkinnedMeshRenderer skinMeshRenderer;
     float newMove = 100f;
 
     void Start()
     {
         skinMeshRenderer = GetComponent<SkinnedMeshRenderer>();
     }
 
     void Update()
     {
 
         if (Input.GetKeyDown(KeyCode.A))
             lerper();
     }
 
     void lerper()
     {
         skinMeshRenderer.SetBlendShapeWeight(0, Mathf.Lerp(0, newMove, Time.deltaTime));
     }
 
 }