How to access predefined in CCS variables from GEL file?

Hello TI engineers.

Could you please tell me how to access the CCS's path variables from GEL file?
My goal is to make a system's call in a GEL file and I want to use relative paths.
For example:
GEL_System("$(PROJECT_LOC)\\MyFile.bat");
GEL_System("$(CCS_BASE_ROOT)\\common\\uscif\\dbgauth.exe");

But on its execution I see an error message in console that PROJECT_LOC or CCS_BASE_ROOT are undefined.
So how to access these predefined in CCS variables from GEL file?

Thanks in advance for your help.
Oleg.