:block.item:= round(dbms_random.value (Min_Value,max_value));
For Ex:
:block.item:= round(dbms_random.value (1, 15));

FUNCTION F_RANDOM
RETURN NUMBER IS
  V_RANDOM NUMBER;
BEGIN
  V_RANDOM := round(dbms_random.value(1, 15));
  return V_RANDOM;
END;

ERROR 201 :'dbms_random.value' must be declared

SQL> CREATE OR REPLACE FUNCTION F_RANDOM
  2  RETURN NUMBER IS
  3    V_RANDOM NUMBER;
  4  BEGIN
  5    V_RANDOM := round(dbms_random.value(1, 15));
  6    return V_RANDOM;
  7  END;
  8  /

Function created.

SQL> select f_random from dual;

  F_RANDOM
----------
        12

SQL>

SQL> declare
  2    l_random_val number;
  3  begin
  4    l_random_val := f_random;
  5
  6    dbms_output.put_line('Random value = ' || l_random_val);
  7  end;
  8  /
Random value = 8

PL/SQL procedure successfully completed.

dbms_random.value must be uesd in the database.I originally thought that it can be used in Forms.

Begin	
:CONTROL.RANDOM_NUMBER:= round(dbms_random.value (1, 15));
End;