How to wait for a button response

I want to make a model for a message box. This message box contains 2 texts and two buttons (ok & cancel). This message box is called from another script. Here I call messageBox method which return boolion. But this message box should wait until the button press. How do I do this?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MessageBoxScript : MonoBehaviour
 {
 
     public float duration = 0.5f;
     private bool btnClicked ;
     private bool result;
     public GameObject panel;
 
    
 
     private void Start()
     {
         btnClicked = true;
     }
 
 
     public bool messageBox(string heading, string body)
     {
         var canvasGroup = GetComponent<CanvasGroup>();
         StartCoroutine(DoFade(canvasGroup, canvasGroup.alpha, 1));
 
         StartCoroutine(waitForResult());
 
         return result;
     }
 
     private IEnumerator DoFade(CanvasGroup canvasGroup, float start, float end)
     {
         float counter = 0f;
 
         while (counter < duration)
         {
             counter += Time.deltaTime;
             canvasGroup.alpha = Mathf.Lerp(start, end, counter / duration);
 
             yield return null;
         }
     }
 
     private IEnumerator waitForResult()
     {
         if (btnClicked == false)
         {
             yield return result;
         }
     }
 
     public void onOKBtnClick()
     {
         Debug.Log("Button clisked " + btnClicked + "");
         btnClicked = false;
         result = true;
     }
 
     public void onClosebtnClick()
     {
         Debug.Log("Button clisked " + btnClicked + "");
         btnClicked = false;
         result = false;
     }
 }