PointCloud reference

Hi, i am writing custom plugin with custom GH types wrapping a PointCloud (custom params etc.) All is working fine when i create a point cloud using custom construct component nad transfer it into custom param, but i need to implement Prompt_Singular and Prompt_Plural.

I have a problem with referencing. All works fine when i create a copy of an object, so i set single point cloud from my gh_param, pick cloud from rhino, and it works but as a copy (geometry in param does not change when i change rhino cloud). How can i reference the geometry using guid/id and notify my param data when it changes in rhino?