Column name as a variable in a database trigger

Question

I am trying to code a pre-insert database trigger to format all varchar2 columns entered into the triggering table. I am using a cursor to get all the relevant column names from all_tab_columns, but do not know how to refer to these values in combination with the ":new" construct within my code. The example below is a very simplified version of what I am trying to do ( it obviously will not work as it is):
declare
cursor column_cur is
select column_name cn
from all_tab_columns
where table_name = 'TEMP_ASSESSMENT'
and data_type = 'VARCHAR2';
v_columnname varchar2(30);
begin
for column_rec in column_cur loop
v_columnname := column_rec.cn;
:new.v_columnname := upper(:new.v_columnname); declare
cursor column_cur is
select column_name cn
from all_tab_columns
where table_name = 'TABLE_X'
and data_type = 'VARCHAR2';
v_columnname varchar2(30);
begin
for column_rec in column_cur loop
v_columnname := column_rec.cn;
:new.v_columnname := upper(:new.v_columnname);
end loop;
end;

Answer 1

Seems to me like the problem in this thread:
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:59412348055
C.