It is the nature of Windows. Until the other process releases the lock on the file, no other processes can touch it. There is nothing you can do except to have your plugin (and any other plugins reading the file) close and release the handle on the file
I do not browse the forums regularly anymore. If you need me for anything (asking questions or anything else), then PM me (be descriptive in your PM, message containing only a link to a thread will be ignored).