Help please!

I want to know how can i put my cbot to open a buying operation and a selling operation at the same time this is the code that i have to open a buying operation "OpenPosition(TradeType.Buy, BuyVolume * 1);" and to open a selling one i have this one "OpenPosition(TradeType.Sell, BuyVolume * 1);" but once i put those 2 codes and the bot tries to open a buying and selling operation it opens one operation either selling or buying and then for the second one an error happens and it says something like order rejected. are those 2 codes wrong? or i have to put a different code if i want to open a selling and buying operation at the same time? what i want the cbot to do is to open a selling and buying operation at the same time. Please help i will really appreciate it.