FUNCTION ISINLOOK()

  Short:
  ------
  ISINLOOK() Checks for existence of a value in a lookup dbf

  Returns:
  --------
  lFound  => value was found

  Syntax:
  -------
  ISINLOOK(expCurrent,nArea,[bCompare],[lBlankOk],[cMsg])

  Description:
  ------------
  Looks for <expCurrent>, and expression of any type,
  in the workarea indicated in <nArea>.

  [bCompare]  - Normally a SEEK would be done, but if
  [bCompare] (a codeblock ) is passed, this acts as a LOCATE FOR ,
  as in LOCATE FOR eval(bCompare)

  [lBlankOk] - If this is false (the default), and
  <expCurrent> is empty, an automatic false is returned.

  [cMsg] - If this is passed, and the value is not
  found ,or is blank and <lBlankOk> is false, this message is
  displayed. Default is no message

  Examples:
  ---------
   @3,0 GET V3 WHEN  !ISINLOOK(v3,5,nil,.f.,"Not Valid or is blank")

   @4,0 GET V4 VALID ;
     ISINLOOK(v4,5,{||adbf->company},.f.,"Not Valid or is  blank")

  Source:
  -------
  S_INLOOK.PRG