Removing a custom profile field when a weblog entry is deleted

<?php
class Add_community
{
    var $settings        = array();
    var $name            = 'Add_community';
    var $version         = '1.0.0';
    var $description     = 'Adds two new member profile fields for each Community weblog entry';
    var $settings_exist  = 'n';
    var $docs_url        = 'http://www.trademarkmedia.com';
    
    // -------------------------------
    //   Constructor - Extensions use this for settings
    // -------------------------------
    function Add_community($settings='')
    {
        $this->settings = $settings;
    }
    // END
    
    // --------------------------------
    //  Activate Extension
    // --------------------------------
    function activate_extension() {
        global $DB;
    
        $hooks[] = array(
            'extension_id' => '',
            'class'        => "Add_community",
            'method'       => "delete_member_field",
            'hook'         => "delete_entries_end",
            'settings'     => "",
            'priority'     => 10,
            'version'      => $this->version,
            'enabled'      => "y"
        );
        $hooks[] = array(
            'extension_id' => '',
            'class'        => "Add_community",
            'method'       => "add_member_field",
            'hook'         => "submit_new_entry_end",
            'settings'     => "",
            'priority'     => 10,
            'version'      => $this->version,
            'enabled'      => "y"
        );
    
        foreach ($hooks as $hook) {
            $DB->query($DB->insert_string('exp_extensions',    $hook));
        }
    }
    // END
        
    // --------------------------------
    //  Update Extension
    // --------------------------------  
    function update_extension($current='')
    {
        global $DB;
        if ($current == '' OR $current == $this->version)
        {
            return FALSE;
        }
        if ($current < '1.0.1')
        {
            // Update to next version 1.0.1
        }
        if ($current < '1.0.2')
        {
            // Update to next version 1.0.2
        }
        $DB->query("UPDATE exp_extensions 
                SET version = '".$DB->escape_str($this->version)."' 
                        WHERE class = 'Example_extension'");
        }
    // END
    
    // --------------------------------
    //  Disable Extension
    // --------------------------------
    function disable_extension()
    {
        global $DB;
        $DB->query("DELETE FROM exp_extensions WHERE class = 'Example_extension'");
    }
    // END
    
    // --------------------------------
    //  Insert up to two Profile Fields
    // --------------------------------        
    function add_member_field($entry_id, $data, $ping_message)
    {
        global $DSP, $DB, $IN, $EXT;
        if ($data['weblog_id'] == '5') {
            $m_field_name = "community_" . $data['url_title'];
            $m_field_label = "Community: " .$data['title'];                    
            $DB->query("INSERT INTO exp_member_fields (m_field_id, m_field_name, m_field_label, m_field_type, m_field_list_items, m_field_ta_rows, m_field_maxl, m_field_width, m_field_search, m_field_required, m_field_public, m_field_reg, m_field_fmt) VALUES (NULL, '$m_field_name', '$m_field_label', 'text', 'No', '10', '100', '100%', 'y', 'n', 'y', 'n', 'none')");
            $DB->query("ALTER table exp_member_data add column m_field_id_{$DB->insert_id} text NOT NULL");                
        }
    }
    // END
        
    // --------------------------------
    //  Delete Profile Fields
    // --------------------------------        
    function delete_member_field()
    {

    }
    // END        
    }
// END CLASS
?>