Update VARCHAR column with an accented string on DB2/AS400 database

I am trying to update a column with an accented string on DB2/AS400
database. The result in the
table is not what I was expecting. I suppose it is a problem of EBCDIC
caracter set.
But what is the solution ?

Here is the code
Begin
    SqlCmd := 'UPDATE PARAMS ' +
                  'SET LIBELLE = ' + QuotedStr( 'aeiou ??????')  +
                'WHERE NOTABLE = 2 ' +
                'AND POSTE = ' + QuotedStr('CHEMINARCHRPT1');
     Execute_SQL( ADOConnect,  SqlCmd);  // Function doing the job
(AConnection.Execute( SqlCmd, cmdText, [eoExecuteNoRecords] );)
End;

After updating the column doesn't contain any accented caracter. Those ones
have been replaced by a small vertical black rectangle.

Cordialement
Rgis CLUSEAU

r.clus...@datasoft.fr