如何判断kbmMWClientQuery是否修改过？

TkbmMWClientQuery有一个属性：IsDataModified,表示记录是否被修改过，实测的结果，当为一个字段赋值一个相同的值时，IsDataModified也会变为True。  

q.Edit;
q.FieldByName('FName').AsString:='test';
q.Post;

象上面的代码，当q.FieldByName('FName').AsString已经等于test时，IsDataMoodified也会由False变为True,这不是我想要的。 

function TDbCache.DataSetIsDataModified(
  akbmMemTable: TkbmCustomMemTable): Boolean;
var
  i: TkbmNativeInt;
  j: TkbmNativeInt;
  pRec, pOrigRec, pOldRec: PkbmRecord;
  aRecords: TkbmList;
  st: TUpdateStatus;
  aOldV, aNewV: Variant;
begin
  if akbmMemTable.State in [dsInsert, dsEdit] then
    akbmMemTable.Post;
  Result := False;
    with akbmMemTable do
    begin
     aRecords := Common.Records;
      for i := 0 to aRecords.Count - 1 do
     begin
       pRec := PkbmRecord(aRecords.Items[i]);
       if pRec = nil then
       begin
         Continue;
       end;
       // Find oldest version.
       pOrigRec := pRec;
       while pOrigRec^.PrevRecordVersion <> nil do
       begin
         pOrigRec := pOrigRec^.PrevRecordVersion;
       end;
 
       // Check what status to react on.
       if pRec^.UpdateStatus = usDeleted then
       begin
         // Dont resolve inserts that were deleted again.
         if pOrigRec^.UpdateStatus = usInserted then
           st := usUnmodified
         else
           st := usDeleted;
       end
       else if pOrigRec^.UpdateStatus = usInserted then
         st := usInserted
       else
         st := pRec^.UpdateStatus;
       pOldRec := OverrideActiveRecordBuffer;
       try
         if st = usModified then
         begin
          OverrideActiveRecordBuffer := pRec; // 指向修改后的数据
           for j := 0 to FieldCount - 1 do
          begin
            OverrideActiveRecordBuffer := pRec; // 指向修改后的数据
            aNewV := FieldByName(Fields[j].FieldName).Value;
            OverrideActiveRecordBuffer := pOrigRec; // 指向修改前的数据
            aOldV := FieldByName(Fields[j].FieldName).Value;
            if aNewV <> aOldV then
            begin
              Result:=True;
              Break;
            end;
           end;
         end
         else if st = usInserted then
         begin
          Result:=True;
         end
         else if st = usDeleted then
         begin
          Result:=True;
         end
         else if pRec.UpdateStatus = usUnmodified then
         begin
 
         end;
       finally
         OverrideActiveRecordBuffer := pOldRec;
       end;
 
       if Result then
         Break;
     end;
    end;
end;