You can use on event "render" that OfflineSurveys fire when showing a question or a Group
You can instruct OfflineSurveys to close survey and consider it as Complete by calling saveResults(true)
Make sure no questions are mandatory, otherwise there will be an error saving the survey
This question cannot be hidden (Always Show this question -> Off)
Your code should look similar to this... also available for download as sample LimeSurvey Question