Thanks
In fact, I had all these documents, and I had quick read of them before I ask question here.
These documents do help, but none of them mentioned about COM and "Mach4.Document".
The only information I found is the "MachRemote" example and one modified from MachRemote
which compiled by mingw and can upload G-code to Mach3.
After a lot of google search ... I think there is no official document for COM, hopefully I'm wrong.
Regards,
KC