Can we deliver an custom message to user in case the expense report is auto-rejected.

We have a requirement where the BPM rule will automatically reject an expense report which will have expense items older than 90 days.

Currently, the rule is rejecting the submitted report but it's not showing why the report is rejected. So Client wants something to notify the cause of rejection to user, something like a customized notification/message to the user for the rejection.

Can you guys help on that.