Lock a Document after response

I have a DB where three people respond to incoming tickets. How can I make it so when one of them has already replied others cannot or get a message stating someone else already has.Thanks

Subject: Lock a Document after response

this is a 2-part solution:1) a computed author field will dynamically set / prohibit further authorship - be sure ‘automatically refresh fields’ is set on the form properties

  1. a hidden field that flags the document as already processed can generate the message — alernately you could use a form event such as querymodechange, look for a field value such as the flagged field and use @prompt

hth