[求助]布林帶的改編

MID :  MA(CLOSE,26);
UPPER: MID + 2*STD(CLOSE,26);
LOWER: MID - 2*STD(CLOSE,26);

以上是金字塔自帶的布林帶公式  想把它改成 突破UPPER就開多  突破LOWER就開空 怎么編寫，麻煩會(huì)的人幫個(gè)忙！謝謝！平倉就是回調(diào)到MID這條線   謝謝！

MID :  MA(CLOSE,26);
UPPER: MID + 2*STD(CLOSE,26);
LOWER: MID - 2*STD(CLOSE,26);

if cross(c,upper) then buy(holding=0,1,market);

if cross(lower,c) then buyshort(holding=0,1,market);

if ref(c>mid,1) and c<mid then sell(1,0,market);

if ref(c<mid,1)  and c>mid then sellshort(1,0,market);