Blessed are you, Lord our God, King of the universe, Creator of heaven and earth. We come humbly into Your presence today on behalf of our brother, Daniel. You are his creator and the Great Physician. If it is Your will, please take this illness from him and allow him to heal. If it is not Your will, please giving him the spirit of grace to boast in his weakness so that the power of Christ may dwell in him as it says in 2 Corinthians 12:8-9 "Concerning this I implored the Lord three times that it might leave me. And He has said to me, “My grace is sufficient for you, for power is perfected in weakness.” Most gladly, therefore, I will rather boast about my weaknesses, so that the power of Christ may dwell in me."
Although we know that it is Jesus who heals the sick, and I don't subscribe the health and wealth brigade, we see that Jesus, in the Gospels, viewed sickness and disease as originating from the devil (see the account of the woman bent over, who He saw was oppressed by the devil, and Him casting a deaf and dumb spirit out of man).
Jesus never said, "Father heal this person if it is your will". He basically said "Be healed", or "Take up your bed and walk". He had authority over sickness and disease. He have given us power of attorney over His Name to use His authority to deal with sickness and disease. We don't have to wonder if it is His will. One sick guy said to Jesus that He could heal him if He wanted to. Jesus said, "I want to", and the guy got healed.
So, have to confidence to assert the authority that the Lord has given you and use the name of Jesus and speak healing to sick people. You can't decide the outcome. Only Jesus can do that, but your statement in the name of Jesus can have amazing results when Jesus honours it with His power.
It may not always happen, but you have been obedient. But if you praying doubting whether it is God's will or not, it will never happen. I'm not putting you down, but exhorting you to stronger faith in the authority that Jesus has given you through the Holy Spirit in you.
By the way, my foundation position is Calvinist Puritan and Sola Scriptura and therefore I know for certain that we believers have authority over sickness and disease. As I said, we can't guarantee that it will always happen, but using our authority and saying "Jesus heals you" gives the best opportunity for a positive outcome.