Microsoft query help

I need this query to have officename is is not null and prompt the user for the officename.  The prompt is what I don't know how to do since there is already "is not" in the criteria.

SELECT Complaints.ComplaintNo, Complaints.CaseName, Complaints.PostSiezure955Date, qryOfficerName.OfficerName, Complaints.TargetDate, Complaints.Stats2
FROM (qryOfficerName INNER JOIN Officers ON qryOfficerName.ContactID = Officers.ContactID) INNER JOIN Complaints ON Officers.ContactID = Complaints.OfficerID
WHERE (((qryOfficerName.OfficerName) Is Not Null) AND ((Complaints.Stats2) Not In ("closed")))
ORDER BY Complaints.ComplaintNo;