db.tt/fOUjj1B9
Here ya go. Very simple change: when you left click, it checks the value of bar.Count, which is how many instances of the bar object there are. If bar.Count = 0, that means there aren't any instances -- so create one, and start stretching that one. If bar.Count > 0, that means there IS one -- so instead of creating one, stretch that one instead.
Hopefully this is what you were looking for!