SUBROUTINE  NLVAL (INDEX, VALUE, MASK)
      INTEGER     INDEX, VALUE, MASK
    
      INTEGER     NLIST (500)   
      INTEGER     NLOC  (500)   
      INTEGER     NTEXT (1500)  
      INTEGER     NTEXTX (500)  
      COMMON   /NARAY/  NLIST   
      COMMON   /NARAY/  NLOC
      COMMON   /NARAY/  NTEXT   
      COMMON   /NARAY/  NTEXTX  
      IF (INDEX .NE. 0) NLIST (INDEX) = IOR (IAND (NLIST (INDEX), NOT (M
     1ASK) ), VALUE)
      RETURN
      END