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


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Month's true start & end
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{ Signals true start & end of month:
   confirms signal at start of following month,
   and signals last day of month in retrospect.}
{ Plot only on daily & intraday charts }

{ ©Copyright 2005 Jose Silva
  The grant of this license is for personal use
  only - no resale or repackaging allowed.
  All code remains the property of Jose Silva.}
{ http://www.metastocktools.com }

{ Start of month }
nuMonth:=Month()<>Ref(Month(),-1) OR Cum(1)=2;

{ End of month }
endMonth:=PeakBars(1,-nuMonth,1)=0
 OR nuMonth=0 AND Cum(1)=LastValue(Cum(1));

{ Plot in own window }
nuMonth;-endMonth

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