Velleman VM204 - Pulse API

Hello, I have several VM204 model boards for sports applications and I would need to use an API to be able to make a pulse and activate a relay for about 2 seconds. I have read on several sites that it can be done by sending 2 APIs (on and off) in a row. But this option does not work for me. Could you tell me how it can be done or how I should modify the firmware to be able to do this. Thanks