Thank you, I have read this, but here I reach the current limits of my knowledge. Once I will know how. I would appreciate every help. My version is at https://sourceforge.net/tracker/?func=detail&aid=3093682&group_id=93107&atid=603140
Just make sure you know how to do multithreading, or this will come back to bite you. (No, incrementing a global variable is not the right way.)