Data Management Mapping question - when two different categories of mapping for the same dimension

I need to set up a Data Management Load rule to transfer data from CPX to FIN cube in a custom Planning application. The source of the mapping must vary based on whether we are mapping an Existing Project or a Placeholder Project from CPX to FIN for the “Business Unit” dimension. Existing Project rolls up to a “Total Existing Projects” node and Placeholder projects roll up to “Total Placeholder Projects” in the hierarchy.

CPX includes Project and Business_Unit, while FIN has Business_Unit but not the Projectdimension. FIN’s Business_Unit granularity is deeper by design. For “Existing Projects”, data maps to a granular business within the FIN cube. For placeholder projects, data in CPX must directly align with the same Business Unit in FIN.