se o codigo tiver um erro digam (a funcao ref referencia dias anteriores)
midrange= Ref((H+L)/2,-1);
Buy = Ref(C,-1)<midrange AND H>midrange ;
BuyPrice = IIf(midrange>O,midrange,O);
Short = Ref(C,-1)>midrange AND L<midrange;
ShortPrice=IIf(midrange<O,midrange,O);
Sell = Short;
Cover = Buy;