In a bowl, take 6 tbsp of orange juice and sprinkle gelatine. Leave it aside for 5 mins to soak.
Now melt it over a pan of hot water till the solution is clear (it should not boil).
Now quickly mix this into remaining orange juice and quickly mix the orange juice-gelatine mixture into the condensed milk mixture. It should be done fast to avoid setting of gelatine into small lumps.
Pour the mixture in a flat tray and set it in refrigerator.