Can I exit from NX post without completely posting my NX part file.
I have tried the exit command in a custom command, however this also closed my NX part file.
I am not sure I understand the question exactly.
If you select a program or operation and postprocess interactively, then you must wait for the post to complete. When it finishes, the status of the program and operations is changed to "Complete". If the part is closed, then the status cannot be set.
You may be better off postprocessing in batch. Then the part is opened, the program posted, status updated, and the part is saved -- all in the background.