Velux window pole useless where can I buy a better one?

I need to open a Velux window it's probably 3 meters high. I bought a pole that extends to 2 meters which I can reach the bar with the hook while standing... However the pole is extending and keeps slipping back inside, there is no way to lock it so useless. Suggestions please for better pole.

I don't want to change window to an electric one either.

This pole I bought...