There is no way to 'loop' the blackstorm via a custom control.
There are two ways to make this happen the way you want.
1. Press the loop on the media manager
2. You can build a play list and add the looping clip into that play list until you reach the desired length of time. Painful if your media is :01 and you need 30mins time.
You could make a custom to recue and play the playlist you created. Then you could nest that into other customs. .... IE, Replay to a tape deck, recue the playlist.... Play the loop custom, replay off
Feel free to contact me if you have any questions.
#Carbonite