Sent to a WIMMessageCallback function to indicate the number of files that were captured or applied.
WIM_MSG_SETPOS wParam = (DWORD) 0; lParam = (DWORD) dwFileCount;
[in] Specifies the number of files that were captured or applied.
Your routine must return WIM_MSG_SUCCESS.
This message is provided primarily for capture operations. For apply operations, use the WIM_MSG_PROGRESS notification.