YOU SAID:
Im going to the next party with him and you
INTO JAPANESE
私は彼とあなたと一緒に次のパーティーに行く予定です
BACK INTO ENGLISH
I will go to the next party with him
INTO JAPANESE
私は彼と一緒に次のパーティーに行きます
BACK INTO ENGLISH
I will go to the next party with him
You've done this before, haven't you.