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


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Calendar Week of Year
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{ Calendar Week of year counter v2.1 }
{ count is independent of any missing chart data }
{ ©Copyright 2003 Jose Silva }
{ http://www.metastocktools.com }

leap:=Frac(Year()/4)=0 AND Frac(Year()/100)<>0
 OR Frac(Year()/400)=0;
y:=Year()*365-715870 {count from 1960}
 +Int(Year()/4)-Int(Year()/100)+Int(Year()/400);
m:=leap+
 If(Month()=2,31-leap,
 If(Month()=3,59,
 If(Month()=4,90,
 If(Month()=5,120,
 If(Month()=6,151,
 If(Month()=7,181,
 If(Month()=8,212,
 If(Month()=9,243,
 If(Month()=10,273,
 If(Month()=11,304,
 If(Month()=12,334,
 -leap)))))))))));
d:=m+DayOfMonth();

{1st day of week in year}
fdy:=Int(Frac((y+.5-leap)/7)*7)+1;

{offset necessary for week start sync}
offset:=If(fdy=3,2,If(fdy=4,3,If(fdy=5,-3,
 If(fdy=6,-2,If(fdy=7,-1,1)))));

Week:=Int(Frac((d+.5+offset)/(374+offset))
 *(374+offset)/7)+1;

Week

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