Dim rs As DAO.Recordset
strSQL="Select ID From MainTableName " _
& "Left Join SubTableName " _
& "On MainTableName.JoinFieldName=SubTableName.JoinFieldName " _
& "WHERE SubTableName.JoinFieldName Is Null"
Set rs=CurrentDB.OpenRecordset(strSQL)
Me.Recordset.FindFirst "ID=" & rs!ID