Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.397
diff -u -p -r1.397 form.inc
--- includes/form.inc	11 Nov 2009 08:52:53 -0000	1.397
+++ includes/form.inc	12 Nov 2009 03:13:41 -0000
@@ -1047,6 +1047,12 @@ function form_builder($form_id, $element
     }
   }
 
+  // Allow for elements to have their process, validate, etc. functions in an
+  // include file.
+  if (!empty($element['#include_file']) && file_exists($element['#include_file'])) {
+    require_once DRUPAL_ROOT . '/' . $element['#include_file'];
+  }
+
   if (!isset($element['#id'])) {
     $element['#id'] = drupal_html_id('edit-' . implode('-', $element['#parents']));
   }