I read this article about using rules and a trigger to populate/create a barcode field from a serial field, tried toy follow it but the screens/ facilities of Drupal 6 seem different for v 7 and the documented steps cannot be replicated. In particular I expected barcodes to be part of the drop down for fields but it isn't
"basically you should add a new rule that fills for you the barcode when new content is created starting from the serial field. The steps are:
create a new rule trigger it on the event: 'after new content is saved' set some condition on the type of the content (optional) use 'populate a field' (under CCK category) as action choose your barcode CCK field Use the token of your serial field : [node:field_YOUR_TOC_SERIAL_FIELD-id] -- I don't remember why I didn't use the token but the follow php code:
array('barcode' => [node:field_MY_FIELD_NAME-id])); ?> If you didn't use Rules before have a look here: http://dev.nodeone.se/node/646 "