FUNCTION AMSUM()

  Short:
  ------
  AMSUM() Sum on a given element of multi-dim array


  Returns:
  --------
  <nSum> => sum of array element

  Syntax:
  -------
  AMSUM(aMult,nElem,[bCondition])

  Description:
  ------------
  Returns sum of array <aMult> element <nElem>.

  [bCondition] is an optional codeblock used to select
  a subset of the  array. This could be used to filter out 0's or
  non-numeric elements.  The block must accept a subarray as a
  parameter, and return  true or false <expL> to determine if this
  element is part of the desired subset. Please note that the
  codeblock accepts the whole subarray, not  just subarray element
  <nElem>

  Examples:
  ---------

   ?"Total file size here is "
   ??AMSUM(DIRECTORY(),2)

   ?"Total .EXE file size here is "
   ??AMSUM(DIRECTORY(),2,{|e|".EXE"$e[1]}  )

   use customer
   ?"Total field size "
   ??AMSUM(DBSTRUCT(),3)

   use customer
   ?"Total CHARACTER field size "
   ??AMSUM(DBSTRUCT(),3,{|e|e[2]=="C"} )

  Notes:
  -------
  Coded by Matthew Maier.

  Presumes all sub-arrays are of equal length

  Source:
  -------
  S_AMSTAT.PRG