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


==================
Signal accumulator
==================
---8<---------------------------

{ Accumulates OBV/Volume (or any other signals)
  between & including two user-input dates }
{ http://www.metastocktools.com }

{signal to accumulate - OBV}
x:=If(C>Ref(C,-1),V,If(C<Ref(C,-1),-V,0));

{signal to accumulate - Volume}
{x:=V;}

StDay:=Input("Start Day",1,31,1);
StMnth:=Input("start Month",1,12,10);
StYear:=Input("start Year",1960,2060,2003);
EnDay:=Input("End Day",1,31,31);
EnMnth:=Input("end Month",1,12,10);
EnYear:=Input("end Year",1960,2060,2003);

start:=Year()>StYear
 OR (Year()=StYear AND (Month()>StMnth
 OR Month()=StMnth AND DayOfMonth()>=StDay));
end:=Year()<EnYear
 OR (Year()=EnYear AND (Month()<EnMnth
 OR Month()=EnMnth AND DayOfMonth()<=EnDay));
period:=start AND end;

If(period,Cum(If(period,x,0)),0)

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http://www.metastocktools.com