I'm not sure I follow. You know the Day of Party but the first meeting should be 2 years before. You're going to set it manually - I am guessing through a constraint. But then you say the day of the party should be scheduled 24 months before. I think what you are asking is for a Start to Finish relationship with a 104 week (I would not use month) lead. The Day of Party is the predecessor and its start drives the finish of the first meeting.