Like Rafacascudo mentioned strart from any existing in Robot code combination which is the closest to your country regulation and modify it according to your needs (create subnatures if needed ; adjust factors ; select \ set fomulas)
Hint: all regulation files are text files so you can also edit them in notepad and have entension rgl.
Default location of them :
c:\Users\All Users\Autodesk\Structural\Common Data\2015\Rgl\
It is recommended to save user rgl file in such folder:
c:\Users\user_login\AppData\Roaming\Autodesk\Autodesk Robot Structural Analysis Professional 2015\CfgUsr\

Rafal Gaweda