7.5.1 Assigning Values with the LET Statement
  The LET statement assigns values to individual array ele-
  ments. For example:
  DIM voucher_num%(100)
      .
      .
      .
  LET voucher_num%(20) = 3253%
      .
      .
      .
  END

  You can also assign values to a portion of an array with the
  LET statement and a FOR...NEXT loop. In the following ex-
  ample, the FOR...NEXT loop assigns zero to array elements
  (1,5) to (1,10), (2,5) to (2,10), and (3,5) to (3,10):
  DIM po_number%(100,100)
      .
      .
      .
  FOR I% = 1% TO 3%
        FOR J% = 5% TO 10%
                  LET po_number%(I%,J%) = 0%
        NEXT J%
  NEXT I%
      .
      .
      .
  END