That is hilarious - but it might actually work (I'll test it out in a bit)...
But to be sure - you mean create a "master thread" and have it spawn the UI thread as well as the worker threads? That way the MASTER can block until all workers come back and somehow notify the UI that it can now proceed to do what needs to be done - all the while not blocking the UI itself...

...wow...
indepth for something I imagined to be a lot simpler...
... lol ...