SUBROUTINE LOOKNR(A,B,V,F,IL)
C
C      NON-RETURNING LOOK-UP (5-81)
C
      DIMENSION B(20),V(20)
C
      J=IL
      M=J-1
      IF (M .EQ. 0) GO TO 24
 22   IF(B(J)-A) 23,24,25
 25   IF(B(M)-A) 26,87,27
 21   IF(B(J)-A)23,24,28
 28   M=J-1
 26   RA=(A-B(M))/(B(J)-B(M))
      GO TO 100
  24   RA=0.0
       M=J
      GO TO 100
 87   RA=0.0
      GO TO 100
 23   J=J+1
      GO TO 21
 27   J=J-1
      M=J-1
      GO TO 25
 100  F=V(M)+RA*(V(J)-V(M))
      IL=J
      RETURN
      END