procedure TForm4.ComboBox1Change(Sender: TObject);
var
i: Integer;
s: String;
l: TListItem;
begin
ListView1.clear;
case ComboBox1.ItemIndex of
 0: s:= 'DE';
 1: s:= 'AUT';
 2: s:= 'SUI';
 3: s:= 'HUN';
end;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'select * from DA42';
ADOQuery1.Open;
   While Not ADOQuery1.Eof do
     begin
        l := ListView1.Items.Add;
        l.Caption := ADOQuery1.FieldByName('Artikel').asString;
        l.SubItems.Add(ADOQuery1.FieldValues['Preis']);
        l.Checked := ADOQuery1.FieldValues[s] = null;
        ADOQuery1.Next;
     end;
end;

if ADOQuery1.FieldValues[s].asbool = True then
        l.Checked := True;