VMS Help FORTRAN, Intrinsic Procedures, IARGCOUNT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  IARGCOUNT ()

  A function that returns the count of actual arguments passed to the
  current routine.  The result is an INTEGER*4 data type.  Note that
  functions with a type of CHARACTER, COMPLEX*16, or REAL*16 have an
  extra argument added that is used to return the function value.