Can a courier take care of my documents at an entry-exit office?

I am in the middle of nowhere in China. With only 30 days allowed per entry, every month I need to either fly out of the country, or go to an entry-exit office in a major city. Can I send my passport and papers via courier? This will save me the hassle of flying to Shanghai.

If you know of a company that handles this sort of business, please let me know!