Supposedly if you put a "sell" order on your stock, it can't be shorted, because it's already for sale (at a higher price). If you put an order in to sell at 50, it's unlikely you're going to get filled. And honestly, if someone wanted to buy my shares at 50 tomorrow, I don't think I'd be upset if they were sold.

You'd want to put a "good till canceled" order in, or you're going to have to keep putting the order in every day. When I've done this in the past, they would ask me every 3 months to renew the order.