Hi to all,

As sugested by Slavek, here it is the tested UDF used to fix the fields with NAN values (compiled with Delphi):

library my_udf;

uses
SysUtils,
Classes;

{$R *.res}

function UDF_IsNan(Number: PDouble): Double; StdCall; export;
begin
Result := Number^;
if (Result <> 0) then
Result := Number^
else
Result := 0;
end;

exports
UDF_IsNan;

begin
end.

These where de SQL expresions used:

DECLARE EXTERNAL FUNCTION IsNan
DOUBLE PRECISION
RETURNS DOUBLE PRECISION BY VALUE
ENTRY_POINT 'UDF_IsNan' MODULE_NAME 'my_udf.dll';

UPDATE my_table SET my_field = IsNan(my_field);

Once more let me say thank you very much for your help.

HDuqueC.