Need Help for Maintenance Cycle Phase change restriction

Hi Experts.

I want to restrict IT Operator user to change maintenance cycle phase further from "Go Live" phase in charm.

By which authorization object, I can restrict user to change the maintenance cycle phase further from "Go Live" phase in charm. I have tried with object /TMWFLOW/M and in Phase Value given only till "Go Live". Still user can change maintenance cycle phase further from go live.

Thanks & Regards

Richa Shrivastava