Intersecting Featurelayer with geometry

Hi developpers,

I am searching for the easiest solution to intersect a polygon Featurelayer with another polygon of given geometry (IGeometry).

With the ITopologicalOperator I managed already to get a list of intersecting polygons and I can calculate areas and area percentages but when I wanted to write them back to the Featurelayer I realized that I do not have the polygon parts situated outside my selecting polygon. I attach a small jpeg explaining what I want.

Thanks for any snippet or hint!

Ralph

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