What is the proper Calculated Dimension Member Syntax

I feel pretty stupid asking this but I haven't had to create a calculated member in quite a while.  If its available can someone provide a link to any documentation or guide me in my formula.

Here is what i'm trying to do. Sum 3 projects as Project A.   We don't want to create a new hierarchy for this so we hoped it could be done in a calculation. 

Project A equals the sum of Project B, Project C, Project D.

We are on BPC 7.5 MS

Thanks!