[... the same main as above ...]
O_Function1:
   [... the same content of O_Function1 ...]
O_Function2:
   [... the same content of O_Function2 ...]
   [... other O_functions ...]
;-- here ends the original code
N_Function1:
   [... some code, sometimes even calling O_Function1 ...]

;JumpTable begins here
  ORG  SomeSuitableFixedAddress
Function1:  jmp   <b>N</b>_Function1
Function2:  jmp   O_Function2
  [etc...]