To remove the ADD item button in the created custom module in the magento admin panel

To remove the ADD item button in the created custom module in the magento admin panel

File path:app/code/local/Samplemod/Samplemod/Block/Adminhtml/Samplemod.php

<?php
class Customer_Customerdetails_Block_Adminhtml_Customerdetails extends Mage_Adminhtml_Block_Widget_Grid_Container
{
  public function __construct()
  {
    $this->_controller = 'adminhtml_customerdetails';
    $this->_blockGroup = 'customerdetails';
  $this->_headerText = Mage::helper('customerdetails')->__('Item Manager');
   // $this->_addButtonLabel = Mage::helper('customerdetails')->__('Add Item');
    parent::__construct();
     $this->_removeButton('add');
  }
} ?>