标题：滑点设置

用户可在下单指令中加减几个最小变动价位:

示例: 

BUY(con1 and HOLDING=0,1,limitr,max(O,REF(HHV(H,5),1))+3*mindiff);
SELL(con2 and HOLDING>0,0,limitr,min(O,ref（LLV(L,5),1))-3*mindiff);