Exclude Multiple Post Thumbnails From Attachments

Hi,

i am trying to exclude multiple post thumbnails from attachments.

i have the following thumbnails setup:

$thumb = new MultiPostThumbnails(array(
    'label' => 'Client Logo',
    'id' => 'client-logo',
    'post_type' => 'clients'
    )
);

$thumb = new MultiPostThumbnails(array(
    'label' => 'Portfolio Home Image',
    'id' => 'port-home-image',
    'post_type' => 'clients'
    )
);

$thumb = new MultiPostThumbnails(array(
    'label' => 'Home Slide Image',
    'id' => 'home-slide-image',
    'post_type' => 'clients'
    )
);

i then have the following code, within the loop to pull in all image attachements and disaply them

<?php
	  $thumb_id = get_post_thumbnail_id( $post_id );
      $args = array(
      'post_type' => 'attachment',
      'numberposts' => $nimg,
	  'post_mime_type' => 'image',
      'post_status' => null,
      'post_parent' => $post->ID,
	  'exclude' => $thumb_id
      );
      $attachments = get_posts($args);
      if ($attachments) {
      foreach ($attachments as $attachment) {
      //echo apply_filters('the_title', $attachment->post_title);
      echo wp_get_attachment_image( $attachment->ID, array (650,650));

     }
      }

?>

this line: $thumb_id = get_post_thumbnail_id( $post_id ); excludes the featured post thumbnail.

any ideas on how i can exclude my 3 other thumbnails?

any help would be greatly appreciated.

Thanks Danyo

http://ww.wp.xz.cn/extend/plugins/multiple-post-thumbnails/