Hi John,
I understand. I do not recommend using an audit for this.
There exists a standard BAdI-Implementation HRPIQ00MODEXAM which does what you want "on the fly" when actvated: Always and instantly when an appraisal is completed or a module booking is cancelled it adjusts the status of the assessment process to an adequate value.
You can activate this example BAdI implementation in SE19. You can also make a copy of it and modify it, because it does not handle the case so well, if thee are more than one cancelled assessment processes. Also check if note 1848971 is implemented in your system. It fixes an issue, when using this process and switching from PIQEVALREGM to appraisal dialog and back.
In your case the BAdI will do the job you want, but only for future appraisals not for those that are already completed. AFAIK there is no standard report doing this, but you can write one of your own using he function module which is also used in the BAdI.
Dirk