Lpc2000

hello friends

i hope you can help me. 

I programmed a bootloader (sector 0) who can check the flashed
application (sectors 1-13) if the application is correct and can flash
a new application or configuration over can0, can1 or serial. After
the start, the bootlaoder starts with a function pointer (when the
check sum calculation is correct) to the startup code of the
application the application. (the bootloader and the application are
two projects, not one hex file). When the application get the message
that it whould be flashed, it must call the programming function in
the bootloader.

I tried to jump from the application directly to the program function
of the bootloader but the startup code of the application overwrite
all variable of the bootloader so that the program function not
correctly work.

My Problem is, how i can tell the bootloader that it is not a normal
start when the application jump with a function pointer back to the
startup code from the bootloader, but it is call from the application
and it go into program mode.

best regards
Tobi

ps.: Sorry my english is not the best. ;-)