The FMEVENT_SELCHANGE message is sent to an extension dynamic-link library (DLL) when the user selects a filename in File Manager's directory window or Search Results window.
lParam
Not used.
This message does not return a value.
Changes in the tree half of the directory window do not produce this message.
Because the user can change the selection many times, the extension DLL must return promptly after processing this message to avoid slowing the selection process for the user.