I've never heard of, written, or performed a spell with this specific purpose, but I will tell you that in my own experience, this is possible, but extremely difficult. I've done it once; I thought I was imagining it, I had an extremely strong will to communicate a message to an estranged friend, and the person on the receiving end was a person I have a very deep, irreplaceable bond with.
So, in the hypothetical situation where you would try to attempt this, you would need to have:
1.) A person you share a strong bond with, perhaps by blood (PM me if you need me to elaborate on what I mean by blood bonds.) You and the receiver need to be psychic.
2.) A strong will, and I mean really strong. This will not work without a purpose. You need to be prepared to go to the end of the world and back for this goal (not literally, of course.)
3.) Both people need to be asleep. You can start out awake, but you need to dream and become lucid. I did this using a WILD (Wake-Induced Lucid Dream.)
I feel like most people will pass this off as useless information without an explanation, so I'll provide my experience. I was having a feud with a very close friend of mine. We were practically sisters. Both of us were psychic, and I believe we had (and still do have) a psychic bond/empathy link. We hadn't talked in a few months. I'd said some things, I'd been rude, and now I was feeling guilty and apologetic. I realized I wanted her back in my life again. I wanted to apologize, but couldn't bear to do it in person- I didn't think she would listen to me if I did.
These thoughts settled into me, and I had a very sudden idea. Would it be possible for me to send her a message in a dream, I thought? I was willing to try, though I doubted heavily I would succeed. I'd never heard of such a story before. I was already skilled in lucid dreaming, so I started a WILD, hoping I would appear in her dream. I did, and from there I could control the events that happened from there.
I'll spare you the gory details. I set up a situation in which she'd reveal how she felt about the fight we had had, how she felt about me, if she wanted to be friends again. After seeing her cry and apologize, I took away the terror of the dream and helped her become (at least, I think- not sure) lucid. We sat and talked, apologizing to each other. I told her if she wanted to be friends again, all she had to do was call at noon the next day.
Here's the crazy part. I could barely believe it when it happened. It wasn't exactly noon- it was 12:03- but she did call. Her first words were, "Hey, you wouldn't believe this crazy dream I had last night. I know you're probably still mad at me, but I miss us being friends. I'm sorry. So this dream..."
She went on explaining exactly what happened in the dream, down to almost every detail! Even thinking about that experience still gives me the chills. I think it was a matter of chance, though; I really doubt I will ever be able to do that again! (By the way, I never told her about my involvement in the dream... I kept it a secret ;))
I have heard from astral projectors that you can enter a person's dream while astral projecting, provided they are asleep and that you can find them. I don't know from experience, but I've heard if you do enter their dream that way, they will appear as if they're drunk, and there's a chance they won't remember you being in their dream.