procedure CreateAppendFile(FileName: string; PSize: int64);
var SFStream, TFStream: TFileStream;
begin
  SFStream:=TFileStream.Create(FileName, fmOpenRead);
  SFStream.Position:=SFStream.Seek(PSize,0);
  try
    DeleteFile(ExtractFilePath(FileName)+'tmp'+ExtractFileName(FileName));
    TFStream:=TFileStream.Create(ExtractFilePath(FileName)+'tmp'+ExtractFileName(FileName),fmOpenWrite or fmCreate);
    try
      TFStream.CopyFrom(SFStream, SFStream.Size-PSize);
    finally
      TFStream.Free;
    end;
  finally
    SFStream.Free;
  end;
end;