Merging columns by sum

[PGriffith]

Not possible with vanilla expressions, but I bet Phil's (free) integration toolkit could do it:

Automation Professionals' Integration Toolkit Module

Automation Professionals is pleased to announce the immediately availability of a major upgrade to its free Simulation Aids Integration Toolkit module. The new feature justifying the "major upgrade" language is the implementation of eleven thirty-one new expression functions which use iteration to accomplish complex transforms of datasets and lists, to or from other datasets and lists, applying filtering, ordering, and computed new columns along the way. While there are certain operations that…