How to insert NOP instruction in the specified address

Hi all

I have a normal 8051's code ,but i want insert NOP instruction in the specified address
without modify the original code (it meaning I didn't need to check LST file to find the address
and then insert a nop )

for example
The code before insert NOP:

02FF F1EA           4147             CALL    A_FUNC
0301 22             4148             RET

The code after insert NOP:

02FF 00             XXXX             NOP
0300 F1EB           4147             CALL    A_FUNC
0302 22             4148             RET

I try to put

ORG 2FFh
NOP

in the top or bottom of the code ,

In the top ,It will be overwritten , there is nothing change,
In the bottom , It will insert a NOP instruction, but destroyed the original instructions format

Does the compiler or linker can help to do this work ??
it also can say I want retain the specified location for NOP,
so compiler will skip it but still compiled correctly

Thanks a lot for you read this post , and please forgive my poor English