Set 2 pending orders:
Order #1
Buy Stop GBP/USD at 1.62497 | SL at 1.62094 | TP at 1.62997
Order #2
Sell Stop GBP/USD at 1.62094 | SL at 1.62497 | TP at 1.61594
Use trailing stop of 15 pips for both orders.
Cancel the orders that didn’t hit (if any) by the end of the current session (UK or US).
