any reason why this wont work?
{exp:channel:entries channel="not diary_event" entry_id="{exp:my_plugin:get_last_edited_entry}”}
get_last_edited_entry function in my plugin is:
function get_last_edited_entry()
{
$this->EE = &get;_instance();
$results = $this->EE->db->query('SELECT entry_id FROM exp_channel_titles ORDER BY edit_date DESC LIMIT 1');
$entry_id = $results->row('entry_id');
return (string) $entry_id;
}