Incident Rule that will trigger update to Contact

Content

I've just created our first transactional survey.  I want to trigger it being sent with an incident rule that will recognize that the incident went from "not solved" to "solved" and was in any of 3 different queues.  The users have asked me to not send a subsequent survey if the contact received one in the last 30 days.  I thought I might do this by updating a "last survey date" custom field on the Contact.  I could check this field in the rule before sending the survey.  But I can't see how to set it.  I'm assuming I would