How to get currency format using pl sql function

Question

Hi all,
I am a newbee on the forum. currently i am facing an issue with the Format of Currency in an rdf report. This is a field of tax amount & i need to make some conditional formatting on this like if the tax amount is Zero then some static note is to be added before this field.
I have tried a lot of functions on it like the one as below:
IF :cp_org_id = 102
AND :invoice_currency_code <> 'CAD'
AND TO_CHAR (NVL (:cf_tax_amount, 0)) = 0
THEN
RETURN (TRUE);
ELSE
RETURN (FALSE);
This is working fine in case of Zero tax amount But gets error out when there some Tax amount exists. It gives a VALUE ERROR in this format Trigger.
Kindly suggest me how to solve this issue with right function. If possible then write the pseudo Code also.
Thanks in advance
D_Verma

Answer 1

In addition to Satyaki:
It might be a 'Reports Thing'.
It works in SQL*Plus (although relying on implicit conversions is a bad idea, as mentioned):
MHO%xe> begin
  2  IF 102 = 102
  3  AND 'DAC' != 'CAD'
  4  AND TO_CHAR (NVL (null, 0)) = 0
  5  THEN
  6  dbms_output.put_line('TRUE');
  7  ELSE
  8  dbms_output.put_line('FALSE');
  9  end if;
10  end;
11  /
TRUE
PL/SQL-procedure is geslaagd.
MHO%xe> begin
  2  IF 102 = 102
  3  AND 'DAC' != 'CAD'
  4  AND TO_CHAR (NVL (0, 0)) = 0
  5  THEN
  6  dbms_output.put_line('TRUE');
  7  ELSE
  8  dbms_output.put_line('FALSE');
  9  end if;
10  end;
11  /
TRUE
PL/SQL-procedure is geslaagd.
MHO%xe> begin
  2  IF 102 = 102
  3  AND 'DAC' != 'CAD'
  4  AND TO_CHAR (NVL ('0', '0')) = '0'
  5  THEN
  6  dbms_output.put_line('TRUE');
  7  ELSE
  8  dbms_output.put_line('FALSE');
  9  end if;
10  end;
11  /
TRUE
PL/SQL-procedure is geslaagd.