How to tune the radius of the circular ring in ADS momentum?

When i want to change the radius of the circular ring , i have to creat another two circles and then perform the "difference" operation. Is there any simple way to realize ring parameters tuning?

I hope that you can use mcurve component from t-lines microstrip library

kspalla, thanks a lot for your suggestion, it does work. But i still have a further question, when i want to creat a complementary split ring resonator (CSRR) in ADS momentum, and i hope the csrr model can be tuned conveniently, what should i do?

This kind of structures requires usage of macros.
this macro can be loaded with ael( application extension language)
There is no short in ADS as of now.

I've never used the "macros", have you got any examples about the application of macro?