The computer freezes when clicking to fast

[newuser]

I'm sorry,
It is on most click events.

Code:

procedure TfmReserveer.lbLessoortClick(Sender: TObject);
begin
  if lbLessoort.ItemIndex >= 0 then
  begin
    lbLessoort.Enabled := false;
    UserSession.qLessoort.Locate('Volgnr', Lesnrs[lbLessoort.ItemIndex], []);
    UserSession.qLessen.First;
    lbLessen.Clear;
    while not UserSession.qLessen.Eof do
    begin
      UserSession.qCheckOfVol.Parameters[0].Value := UserSession.qLessenVOLGNR.AsInteger;
      UserSession.qCheckOfVol.Parameters[1].Value := DatumVanLes;
      UserSession.qCheckOfVol.Open;
      if UserSession.qCheckOfVolaantal.AsInteger >= UserSession.qLessenMAXAANTAL.AsInteger then
        lbLessen.Items.Addpair(weekdagen[UserSession.qLessenDAG.AsInteger] + ' ' + UserSession.qLessenSTARTUUR.AsString + ':' + PadLeft(UserSession.qLessenSTARTMIN.AsString, 2, '0'), 'vol')
      else
        lbLessen.Items.Add(weekdagen[UserSession.qLessenDAG.AsInteger] + ' ' + UserSession.qLessenSTARTUUR.AsString + ':' + PadLeft(UserSession.qLessenSTARTMIN.AsString, 2, '0'));
      UserSession.qLessen.Next;
    end;
    lbLessoort.Enabled := true;
  end;
  lReserveer.Caption := '';
  bReserveer.Enabled := false;
end;

Thank you for your quick respons!