Is your data in one of your tables dependent on other tables?
I often see this where people have linked tables, but are missing information in all of the fields
Check out this sample of your Db
I added a casestatus table and created a new query called open cases and based your listbox off of that
EDIT: Essentially I did what David suggested.
What exactly are you not following? Maybe i can explain it alittle better
In the last query you would add a where statement
so something like
where qryCoursesTaken.staffnumber= some number