example1.php

$product = Mage::getModel('catalog/product')->load($id);

$groupPrice = $product->getData('group_price');

$product->setData('group_price',array (
	    array (
		"website_id" => 0,
		"cust_group" => $cutGrpId,
		"price" => $arrprice['someprice']
	    )));
	
	try{	    
	   $product->save();
	  }catch	(Exception $e)
	    {	   
	   
	    Mage::log(print_r($e,true), NULL, 'my_exception.log',true); 
	    }	    
	}