Update a table from a query

[ccocom]

I have a database that tracks student issues. Each issue in this database is either "open" or "closed." When the user opens the form that allows her to edit or "close" an "open" issue, a modal popup dialog box requires her to choose from a combo box list of students who have open issues. The row source of the combo box is a query, containing only open issues. The problem I am having is how to keep the combo box up to date without having duplicate records (if one particular student has multiple open issues). I have tried to append this query to a table that does not allow duplicates and then to base the combo box on the table; this solves the duplicates issue, but fails to keep the list current as all students who have ever had an open issue are listed. I think that if I precdeded the append query with a delete query, first eliminating all students with only closed issues, I would achieve my purpose, but I am guessing that there is a much easier way to proceed. Any ideas?