I am sorry, but this goes against my ethics. Casting a spell to influence the lessons that may be learned from this experience is wrong. This is something Josiah needs to go through, in my opinion. As his friend, I would suggest talking to him about his affection, and just being there for him. If he wants the spell cast on him, mention it, and if he says yes then I would say it is fine to cast the spell, however, if he says no, let it be. If you cannot establish communication with josiah about this, then take that as a no, and let it be. I understand your concern, and I gurantee he appreciates how much you care for him.
This is alos a terrible thing to wish on sombody. Love is a vital emotion in everyones life, and it is the emotion linked with the heart chakra. By even wishing this upon somebody, it could throw them out of balance internally, and can cause some major depression. This is just a bad idea altogether. Sorry.