проблемы с фильтрацией!!

procedure TForm1.Button6Click(Sender: TObject);
var flag2:boolean;
begin
flag2:=false;
If DateTimePicker1.Date>DateTimePicker2.Date then flag2:=true;
Table2.Filter:='';
if CheckBox1.Checked
then Table2.Filter := 'Dat >= ''' + DateToStr(DateTimePicker1.Date) + '''';
Showmessage(Table2.Filter);
if CheckBox2.Checked then
begin
if Table2.Filter <> '' then Table2.Filter := Table2.Filter + ' and ';
Table2.Filter := Table2.Filter + 'Dat <= ''' + DateToStr(DateTimePicker2.Date) + '''';
end;
 Showmessage(Table2.Filter);
if CheckBox3.Checked then
begin
if Table2.Filter <> '' then Table2.Filter := Table2.Filter + ' and ';
Table2.Filter:= Table2.Filter + 'Num = ''' + ComboBox2.Text + '''';
end;
Showmessage(Table2.Filter);
If flag2=false then Table2.Filtered:=true else;
end;