I had a thought
I can send a command over the modem and the controller resets itself upon receiption of this command then boot loader program is activated!
Once the modem is online and connected i expect i can use it as if my circuit is connected directly to the com port of the pc.
The only problem left is to modify the windows flash program to dial a modem rather than use direct com connection unless i find a free software which already has this option.
I think it will be best for me to re-invent the wheel and write both portions of the bootloader code that resides in both the flash and the pc unless there is a freewhere version of both with source code that i can modify myself.
Mahmood