Lpc2000

Hi,

for an in-system update of the firmware i have the following idea:
1. store the new firmware in an external serial flash
2. allocate memory in RAM with malloc() for the update function
3. copy update-function from ROM to RAM
4. call update-function in RAM
5. update-function copies firmware from external serial flash to 
internal flash with IAP commands

My question is, how code can be executed in RAM.
How can i call a function in RAM?
Thanks for all hints.

Regards
Arvid