I'm not 100% sure if I understand what you mean.
The spell cures the same as before. So, during the spell casting the healer decides what to heal. He then calculates how long it will take that everything is cured (this will be a few minutes for major or hours for minor healing). If the patient interrupts the healing process for any reason it stops and there is no further curing until a new Healing spell is cast. Everything healed so far remain healed (except of bleeding, which reopen).
I hope this answers your question.