I have a list (list1) which contains many Projects.
Every project consists of many sub-projects which are located in another list (list2).
I am using lookup to link each sub-project (in list2) to its parent project (in list1).
What I want is: to automatically change the status of a certain project (in list1) to SHUTDOWN when all the related sub-projects (in list2) are SHUTDOWN.
e.g: Project1 (in list1) contains sub-projectA and sub-projectB. When I update sub-projectA and sub-projectB to SHUTDOWN, I want Project1 to be automatically updated to SHUTDOWN too.
What would be the simplest way to do this?