How to convert long filenames in short filenames

uses
  Windows, SysUtils;

function GetShortName(sLongName: string): string;
var
  sShortName:    string;
  nShortNameLen: Integer;
begin
  SetLength(sShortName, MAX_PATH);
  nShortNameLen := GetShortPathName(PChar(sLongName), PChar(sShortName), MAX_PATH - 1);
  if (0 = nShortNameLen) then
  begin
    // handle errors...
  end;
  SetLength(sShortName, nShortNameLen);
  Result := sShortName;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Caption := GetShortName('C:\Program Files\Delphi6\Lib\test.cnt');
  // --> C:\PROGRA~1\Delphi6\Lib\test.cnt
end;