Using define_column when number of columns are varying

[Quoted]    I am writing a package using DBMS_SQL.I build a select statement using the table name and the Keys supplied by the user.I select the columns from cols and build the select statement.So my select statement has varying number of columns.Lets assume that the data Types of these columns are CHAR,NUMBER and DATE.So how do i Use the DEFINE_COLUMN procedure.I cant declare variables offhand.

                Please i request suggestions as early as possible.Please
write to me at Madhushekhar_at_bosch.com.
                Thanks in advance.
                                                                           
                        Regards Madhu Shekar
                                                                           
                        Bangalore