[quote="leo"]There's no need to mess around with tabs, or show the collection in a window at all, just to modify a collection.
See the Scrap Collection toolbar for examples.[/quote]
Yes, thanks for the hint.
But I need the collection on the screen (in the destination pane) when collecting files (in the source pane) since the collection is created incrementally/manually.
However, your solution based on dopusrt.exe works fine for me. Thanks again for the quick answer.