As far as I can understand from your story, you can't do it right now, unless Binance has new order types. What you can do is probably put a sell order at the price you believe Bitcoin will reach later on, and then put the stop loss at $50k. If the price drop to $50k then your order will be placed on the order book and if you're lucky all of your Bitcoin might get sold asap. If that's not your thing, then another option is to use a bot that supports such task.