sql startment problem PLEASE HELP .....

Hi all,

I am using Oracle8i Enterprise Edition in window 2000

my problem as following



~~~~~~~~~~~~~~~~~~~~~

SQL>  create table ttt 2   ( name varchar2(100)  3   , 4   constraint e check (name = lower(name)));

Table created.

SQL> alter table ttt 2  modify constraint e 3  check (name = upper(name));
check (name = upper(name))
*
ERROR at line 3:
ORA-00933: SQL command not properly ended


How can I modify constraint e ???? 
                                 thanks.