diff --git a/booking.import_data.inc b/booking.import_data.inc
index 6590e70..1fcb373 100644
--- a/booking.import_data.inc
+++ b/booking.import_data.inc
@@ -85,6 +85,11 @@ function booking_import_data_admin_submit($form, &$form_state)
 	$datetime_fields = array('booking_outflight_origin_ts', 'booking_outflight_destination_ts', 'booking_rtrnflight_origin_ts',
 						'booking_rtrnflight_destination_ts','booking_dob', 'booking_passport_expiry_date');							
 	$builtin_fields_to_import = array('nid');
+
+	// These are fields we can use to key the update
+	$unique_fields = array('nid', 'booking_tempid');
+	$update_key = "";
+
 	//$custom_fields_to_import = explode(";", variable_get('booking_import_include_fields', ''));
 	$data = $form_state['input'];
 	$import_fields = $data['booking_import_data_fields'];
@@ -136,7 +141,20 @@ function booking_import_data_admin_submit($form, &$form_state)
 		$studygroups_update_array = array();
 		$studygroup_roles_update_array = array();
 
-		//do some error checking
+		// Check that there is a key we can use to perform the update
+		foreach ($unique_fields as $key) {
+			if (array_key_exists($key, $record)) {
+				$update_key = $key;
+			}
+		}
+
+		// Check that we found a key, otherwise the update can't be processed
+		if ($key === "") {
+			drupal_set_message("Error: Unable to locate any unique identifier in input file for record number $update_counter.", 'error', FALSE);
+			break;
+		}
+
+		// Pre-process some data
 		foreach($fields_to_import as $field) {
 			//make sure to skip the nid field since we can't update that
 			if ($field == 'nid') {
@@ -175,14 +193,15 @@ function booking_import_data_admin_submit($form, &$form_state)
 			}
 		}
 
+		// Perform the actual update
 		if (count($update_array) > 0) {
 			$query = db_update('booking_person')
 			  ->fields($update_array)
-			  ->condition('nid', $record['nid']);	
+			  ->condition($key, $record[$key]);
 		
 			$rows = $query->execute();
-			
-			$update_messages[] = t("Update Query:<br />@info<br />Condition: @nid<br />Rows affected: @rows<br />Values: <br /><pre>@values</pre>", array('@info' => (string) $query, '@nid' => $record['nid'], '@rows' => $rows, '@values' => print_r( $update_array, true) ));
+			$update_messages[] = t("Update Query:<br />@info<br />Condition: @nid<br />Rows affected: @rows<br />Values: <br /><pre>@values</pre>", 
+				array('@info' => (string) $query, '@nid' => $record[$key], '@rows' => $rows, '@values' => print_r( $update_array, true) ));
 		}
 		
 		//handle study group processing