Как подсчитать занимаемое директорией место

var
  DirBytes: integer;

function TFileBrowser.DirSize(Dir: string): integer;
var
  SearchRec: TSearchRec;
  Separator: string;
begin
  if Copy(Dir, Length(Dir), 1) = '\' then Separator := ''
  else Separator := '\';
  if FindFirst(Dir + Separator + '*.*', faAnyFile, SearchRec) = 0 then begin
    if FileExists(Dir + Separator + SearchRec.Name) then begin
      DirBytes := DirBytes + SearchRec.Size;
      {Memo1.Lines.Add(Dir+Separator+SearchRec.Name);}
    end
    else
      if DirectoryExists(Dir + Separator + SearchRec.Name) then begin
        if (SearchRec.Name <> '.') and (SearchRec.Name <> '..') then
          DirSize(Dir + Separator + SearchRec.Name);
      end;
    while FindNext(SearchRec) = 0 do begin
      if FileExists(Dir + Separator + SearchRec.Name) then begin
        DirBytes := DirBytes + SearchRec.Size;
        {Memo1.Lines.Add(Dir+Separator+SearchRec.Name);}
      end
      else
        if DirectoryExists(Dir + Separator + SearchRec.Name) then begin
          if (SearchRec.Name <> '.') and (SearchRec.Name <> '..') then begin
            DirSize(Dir + Separator + SearchRec.Name);
          end;
        end;
    end;
  end;
  FindClose(SearchRec);
end;