Hi, Can I use the AddAPI macro as it is to declare procs that I write my self or
can the endp macro be extended to use that directly?

This could really make the source easier to read and understand.
Can the AddAPI macro allso be extended so that we can specify
calling convension to be used. Maybe it could have some default
using what it does now.

Are there a compleete description somewhere where I can read about how to
design my own 'advanced' macros. I.e what does common mean and what it does.

Start with reading the flat assembler manual.