Can demon counter a demonic possession of another person?

Oh yes they can. It happened to me after my idiotic friend summoned a greater demon with a Ouija board while i was in the room. It possessed me for some reason i can't understand. I had to deal with him/her (never figured out the sex, it wouldn't tell me) for months and it was indubitably pissed at me for having a strong will. I named him/her Fuzzy which annoyed it to no end. We did not have a friendly relationship, let me tell you, Fuzzy gave me fits of rage around my friends, and i sometimes became violent. It was fun annoying it but the thing really was a head case, always rambling on riotously about blood and killing. Eventually after hitting my uncle over the head with a toaster my mother (who happens to be a devout Christan) demanded to know what was going on with me. I told her and she kicked me out for dabbling in the occult. So to redeem myself i went to a catholic priest who got me in touch with an exorcist. He failed to pull it of, instead Fuzzy freaked out tried to make me bite his throat. I resisted and ran out. Weeks later i ran into some crazy who claimed to be a Golden Dawn (whatever that is) sorcerer or whatever and he told fuzzy off for entering a body without a proper contract. Fuzzy refused to leave so the dude set up some freaky ritual and summoned a big-shot demon named Amon who apparently frowned upon "improper contracts with a human host" cause he dragged fuzzy out of me and that was that. The sorcerer told me that i was lucky i had such a strong will and said i would make a worthy member of his freaky group. I graciously refused, i want nothing to do with magic or demons, hell i just got mom to let me back in the house, it was hard to stay in college while living at my partying friend's house. So yeah, its possible, but don't suggest trying it unless you get an expert to help.