UpdatePanel does not update

I have a simple page with an HtmlInputHidden field. I am using Javascript to update this value, and when posting back the page, I want to read the value of this HtmlInputHidden field. The Value property of this HtmlInputHidden field returns the default value (the value it had when the page was created, not the value rendered through Javascript). I also tried registering the HtmlInputHidden field with ScriptManager.RegisterHiddenField (page, "MyHtmlImputHiddenField", "initialvalue"), but it still allows me to read the "initial value" even though I (via javascript) can verify that the value has changed.

I tried to hard-code the rowid, and to my surprise, after the postback gridview was exactly the same before deleting, but the record was deleted from the database. (I named the method of data binding).

  protected void gridViewDelete(object sender, GridViewDeleteEventArgs e)
  {

      bool bDelete = false;
      bool bCheck = false;

      if (hfControl.Value != "1")
      {
          // check relationship
          bCheck = validation_method(.......);
          if (bCheck)
          {
              bDelete = true;
          }   
      }
      else
      {
          hfControl.Value = "";
          bDelete = true;
      }

      if (bDelete)
      {
          //process delete
      }
      else
      {
          string script = string.Empty;

          script += " var x; ";
          script += " x = confirm('are u sure?'); ";
          script += " if (x){ " ;
          script += " document.getElementById('hfControl').value  = '1'; ";
          script += " setTimeOut(__doPostBack('gridView','Delete$"
                                      + e.RowIndex + "'),0);";
          script += " } ";

          ScriptManager.RegisterClientScriptBlock(this,
                                       Page.GetType()
                                       , "confirm"
                                       , script
                                       ,true);
      }
   }