OK - I have it,
for this I've set up a Scheduled Job that fires off to "attended" participants a few days after the event. I set up a smart group of "participants whos participatory date was after [a month ago]" so i didn't spam older participants, and used the group as an "include" filter.
Set up an event, of the right type, so that it would get fired.
Added contacts to the event (and gave them the "Attended" status.
Created the webform and including (from the CiviCRM tab):
- existing contact
- firstname
- lastname
- contact ID
- checksum
then in the "Event Registration" section
- show past events: all
- Registration Options > Disable unregistering participants: yes
- Registration Options > Allow events populated from URL: yes
- under Contact1
- no of event sets for contact1: 1
- event(s): User Select
- & any needed participant custom fields
and build the checksummed url:
http://example.com/node/xxx?event1={event.event_id}&cid={contact.contact_id}&checksum={contact.checksum}
think that's it.
let me know if I missed a bit (or did anything stupid!) and I'll correct it.