Loading classes from different components?

Hi,

I understand that my portal component can instantiate (API)-classes of all components referenced in the (Private)SharingReference of portalapp.xml. But my problem is I don't know in advance what classes from which .pars my component is going to instantiate via reflection, so I can't put them into the SharingReference.

My question: how can I tell the classloader during runtime, not deploy time, to dynamically load a different portal component?

Any hints are very welcome.

Regards

John