enum ListLoaderEnum {LL_RESET, LL_KILLLOAD};

class MainWin : public WithMainLayout<TopWindow> {
protected:

	StaticMutex loadListLock;
	Thread listLoaderThread;
	volatile Atomic stopFetchingTags; 

public:
	MainWin() : stopFetchingTags(0)	{

	virtual void Close() {
		// While we are in the Close event, no threads can continue, so a Wait will lock up the system
		// Notify threads to stop, then trigger a callback
		int x = listLoaderThread.GetCount();
		if (x) {
			loadListLock.Enter();
			stopFetchingTags = LL_KILLLOAD;
			loadListLock.Leave();
			this->ProcessEvents();
			Sleep(100);
			PostCallback(THISBACK(Close));
		} else {
			TopWindow::Close();  // Won't close unless this is called
		}
	}

	void EnrichDbFromTags() {
		listLoaderThread.Run(THISBACK(EnrichDbFromTagsThread));
	}

	void EnrichDbFromTagsThread() {
		stopFetchingTags = LL_RESET;
		
		...

		while(lst.Fetch()) {

			if (stopFetchingTags == LL_KILLLOAD) {
				break;
			}
		...
		}
	}