One possible solution I think, using triggers: procedure TMainForm.UniCheckComboBox1TriggerEvent(Sender: TUniCustomComboBox; AButtonId: Integer); var I: Integer; begin if AButtonId = 0 then begin for I := 0 to (Sender as TUniCheckComboBox).Items.Count-1 do (Sender as TUniCheckComboBox).Selected[I] := True; (Sender as TUniCheckComboBox).JSInterface.JSCall('fireEvent', ['select', (Sender as TUniCheckComboBox).JSControl]); end else if AButtonId = 1 then begin