[amibroker] long only rotational

[upsidetarget]

I want to use a simple RS system, but back testing shows long AND short trades. 
How can I limit results to long trades only?

Thanks

EnableRotationalTrading(); 
SetOption("WorstRankHeld",5); 
PosQty = 5;
SetOption("MaxOpenPositions", PosQty );
PositionSize = -100/PosQty;
PositionScore= (ROC(C,252));