BLICUROVL
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  Function : Current Overlay Number

  Syntax   : nuVal = BLICUROVL()

  Return   : Current overlay number for identification purposes

  This function returns the overlay number of the current overlay, which
  corresponds to the overlay number displayed in the MAP file after the
  name of an overlaid segment. It can be used to identify the name of the
  currently executing overlay.

  Example  :
  * Get the overlay number of the current overlay
  *
  ? "The current overlay number is " , BLICUROVL()