StrFormatByteSize64: how to use it?

Hello.

I need to format a string in order to show the size of a file sized 10 GB. The string should be formatted in Explorer way, so it should show "10,0 GB". I used StrFormatByteSize (within shlwapi.dll) and this function has always worked fine, but if you need to format an Int64 value (a file sized over 2 GB), the function stops and it doesn't convert the value.
I discovered that I must use StrFormatByteSize64 and I implemented in the following way:

unit MyUnit;

.....

{$EXTERNALSYM StrFormatByteSize64}
function StrFormatByteSize64(
    qdw: int64;
    pszBuf: PCHAR;
    uiBufSize: UINT
):PCHAR; stdcall;export;
{$EXTERNALSYM StrFormatByteSize64A}
function StrFormatByteSize64A(
    qdw: int64;
    pszBuf: PAnsiChar;
    uiBufSize: UINT
):PAnsiChar; stdcall;export;
{$EXTERNALSYM StrFormatByteSize64W}
function StrFormatByteSize64W(
    qdw: int64;
    pszBuf: PWideChar;
    uiBufSize: UINT
):PWideChar; stdcall;export;

function StrFormatByteSize64; external 'shlwapi.dll' name 'StrFormatByteSize64A';
function StrFormatByteSize64A; external 'shlwapi.dll' name 'StrFormatByteSize64A';
function StrFormatByteSize64W; external 'shlwapi.dll' name 'StrFormatByteSize64W';

....

procedure TForm1.DimFile(Siz: Int64): string;
var
filesize: PAnsiChar;
begin
StrFormatByteSize64(Siz, FileSize,255);
....
end;

When I execute this program StrFormatByteSize64 converts the value to string, but it raises also an "Access Violation" error.

Please, could you explain me where am I wrong?
I am using D7 and Windows XP SP2

Thank you very much :D

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Matteo Riso
http://www.zipgenius.it
Happy ZipGenius User #1
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