To use the extension, your origin program must create a directory with the following path:
<something>\{83120B49-8EFA-4CDE-8AFD-2954AE52B4A3}.<HWND>
where <HWND> is the destination program's HWND.
The actual path doesn't matter as long as it points to an existing directory. (Explorer won't run the shell copy hook otherwise)
The extension will send back a WM_COPYDATA message containing the destination path.