DEVELOPMENT OF A NINJATRADER STRATEGY

Hello there, i need to develop indicator/ea for ninjatrader that will allow me to set a different stoploss per multiple assets or pairs at the same time no matter how many contracts i open, if i choosed 300$ stoploss no matter how many contracts i opend it should close all of the positions , for example lets say i trade 3 pairs EURUSD, USDJPY and GBPUSD, i set EURUSD stoploss 300$ , USDJPY 400$ and GBPUSD 200$ , i trade all of them at the same time when one of them reach the stoploss that i set it should close all of the positions of the same asset or pair and the rest should keep trading