a question about permission setting in process runtime

I set up a RTC2.0.0.2 server.

I read through this article:
Process behavior lookup in Rational Team Concert 2.0
http://jazz.net/library/article/292

My project is fairly simple: a Dev team under project area. The team's timeline is Main Development.
The project's timeline hierarchy is Main Development->Release 1->Sprint 1.

I have a "Release Plan" , planned for "Release 1" ,owned by "Dev Team". The plan's type is "Team Release Backlog"
I have a "Sprint Plan", planned for "Sprint 1" ,owned by "Dev Team". The plan's type is "Sprint Backlog"

I know how to enable/disable someone to update a plan.

My question is, how can I achieve this effect:
someone, say Team Member of "Dev Team", can update "Sprint Plan", BUT can not update "Release Plan"?

thanks!