MetaStock -> Tools -> Indicator Builder -> New
Copy and paste formula below.


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2-point plot
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{ 2-point plot, coding example v2.5 }
{ Trendline choice 1: last High/Low in month }
{ Trendline choice 2: lows at Jan/June 2004 }
{ ©Copyright 2003-2004 Jose Silva }
{ http://www.metastocktools.com }

plot:=Input("choose event trend [1~2]",1,2,1);
choose:=Input("plot: trendline [1],  event points [2]",1,2,1);

{define events}
time1:=C=HHV(C,21);
time2:=C=LLV(C,21);
time2:=time2 AND time2<>time1;

{alternative events}
dateA:=Year()=2004 AND Month()=1;
dateA:=If(LastValue(Cum(dateA))=0,
 Year()=LastValue(Year())-1
 AND Month()=LastValue(Month()),dateA);
LoValA:=Lowest(ValueWhen(1,dateA,L));
timeA:=dateA AND L=LastValue(LoValA);

dateB:=Year()=2004 AND Month()=6;
dateB:=If(LastValue(Cum(dateB))=0,
 Year()=LastValue(Year())
 AND Month()=LastValue(Month()),dateB);
LoValB:=Lowest(ValueWhen(1,dateB,L));
timeB:=dateB AND L=LastValue(LoValB);
timeB:=timeB AND timeB<>timeA;

{choose events}
time1:=If(plot=1,time1,timeA);
time2:=If(plot=1,time2,timeB);
price1:=If(plot=1,C,L);
price2:=If(plot=1,C,L);

{restrict to last events}
time1:=time1
 AND Cum(time1)=LastValue(Cum(time1));
time2:=time2
 AND Cum(time2)=LastValue(Cum(time2));

{sort events}
t1pds:=LastValue(BarsSince(time1));
t2pds:=LastValue(BarsSince(time2));
x1:=If(t1pds>=t2pds,time1,time2);
x2:=If(t1pds>=t2pds,time2,time1);
y1:=If(t1pds>=t2pds,price1,price2);
y2:=If(t1pds>=t2pds,price2,price1);

{fix coordinates}
y1:=ValueWhen(1,x1,y1);
y2:=LastValue(ValueWhen(1,x2,y2));
b1:=LastValue(BarsSince(x1));
b2:=LastValue(BarsSince(x2));

{trendline definition}
plot:=y1+BarsSince(x1)*(y2-y1)/(b1-b2+.000001);
plot:=Ref(Ref(plot,-b2),b2);{rem to extend plot}

If(choose=1,plot,time1+time2)

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