life cycle control

we are create the life cycle asdesign,checker,approval,released,ecn etc. How to prevent user tochange the life cyle design to approval,released and ecn.
the user has to change the life cycle only next state.

Ex
Requirement

design to Checker

checker to approval

Thanks and regards

S.Mahendran
Premier Evolvics Pvt Ltd
IndiaSolidworksWorkgroup Pdm