programe flash of the 89C51 over RS-232

Hi all,
I am a newbe, so sorry if my question to this forum might be totally
misplaced.
What I have got:
I got an ATMEL 89C51CC01UA-IM controlling a device. I also have a
Windows-Software communicating with the controller via RS-232 with my
own protocoll.
What I want to do:
I want to flash the microcontroller from within my own Windows-Software
(just like the FLIP-Software).

I found an ATMEL Paper (ANM088) "In-System Programming - Serial
Protocol Stack for C51 Products" which explains the protocol.
My problem is, I don't understand too much of this paper. Can some1
help me?
Maybe some1 has dealed with the same problem.

Thanks, Joerg.