VMS Help PASCAL, Predeclared Routines, Allocation, BYTE_OFFSET  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The  BYTE_OFFSET  function  returns  an   integer   value   that
  represents the byte position of a field in a record.

  Syntax:

     BYTE_OFFSET( t,f )

  The parameter 't' can be of any record type or variable, and the
  parameter 'f' can be any field contained in that record.