I need a script to reverse position

Hi there, I need a script that reverses an existing position at a certain price point. For example; I have a long position on a stock with 1000 shares, I want it to reverse at a price point x, so it has to close that long position at that certain price and open a short position with 1000 shares. or if I have a short position it has to close the short position and open a long position.