Customclientfield value Please help

[Cled]

Hi ,

 

 

 

i am making a hook which will check if the value entered by client in customfield is unique , and is not duplicate.i dont know how to get value entered during checkout in customfield.

 

<?php

function custom_value($param) { 
                               global $errormessage;
                               $q = "SELECT COUNT(*) FROM `tblcustomfieldsvalues` WHERE value='$customfields'";
                               $result = mysql_query($q); 
                              if (mysql_num_rows($result)>0)  {
        return $errormessage .= "<li>Username Already Exists , Please choose Another Username";
   }
} 
add_hook("ShoppingCartValidateProductUpdate",1,"custom_value");
?>

 

thanks