Mailing list for incomplete courses

I know we can create an Acymailing list of people who are enrolled in a specific course.
However, I am wondering if there is a way to narrow that down.

What I would like to do is to divide this into
a) a list of people enrolled in a specific course, who have not yet passed the exam or completed the course, so I can remind them to complete the course before I expire it.
b) send out an email upon course completion inviting them to review and offer them a coupon on a different course.

Thanks.

I guess you would know that this feature is not currently in Joomdle. Even if it was to be built the process would need to be determined. Eg. How do we know when a course is not completed? I see a few potential options , let me know if you are thinking something different:

1) Enroll in course --> add to mailing list
2) Complete course --> remove mailing


Issue #1
The above assumption is that Moodle will trigger a course completion for us - which I do not believe it will do. Therefore under the assumption that Moodles does not, there would need to be a cron job to compare users in a list against those in a course to see if the students have completed.

Issue #2
How does Moodle know if a course is completed? If I recall correctly, course completion happens in two ways:
1) Students manually mark the course as completed. Therefore you run the risk that the students do not mark the course as completed and thus will be on the mailing list.
2) You define some activity as once completed Moodle determines the course is completed.

I have two goals.
1. to remind people that they have enrolled in a course and that they need to complete it.
2. to send people a coupon for a second course after they have completed the first.

Number 2 is more significant for me.

For me the completion of a single activity is equal to course completion. In my case it's enough for the completion of that activity to trigger the switch.

However the problem I have with the suggested situation is that I wouldn't have a mailing list of people who have completed the activity. Although that is not particularly necessary as long as the activity completion also sends a 'congratulations' email.

I'll look through moodle to see if they have any answer for this.