input: PeriodsAgo(numericsimple);

var: 	cl(0),hi(0),lo(0);

cl = CloseD(PeriodsAgo+1);
hi = HighD(PeriodsAgo);
lo = LowD(PeriodsAgo);

TrueRangeD = maxlist(cl,hi) - minlist(cl,lo);