just created a blank subform
You cannot just create a blank subform control without a source object. You need to build the form or query first. If you want this in datasheet view simply build the query definition and save the query. Use the query as the source object of the subform. Get rid of the where clause
"SELECT tblTAppt.TRef, tblTAppt.UID, tblTAppt.ApptStart_Dt, tblTAppt.ApptStart_Dt, tblTAppt.ApptEnd_Dt, tblTAppt.AppointedBy, tblTAppt.JobPosition, tblTRank.HDesc FROM (tblTAppt INNER JOIN tblTutor ON tblTAppt.TRef = tblTutor.TRef) INNER JOIN tblTRank ON tblTAppt.RankCode = tblTRank.ID ORDER BY tblTAppt.ApptEnd_Dt DESC"
Now link the subform to the listbox using the link criteria
Master Link Fields: [lstTutor]
Child Link Fields: [TRef]
Now when you make a selection in the listbox the subform will automatically filter.