Datamodel question

Hello everybody,


I need to develop a datamodel which contains 'milestones'.

In our company we have Three milestones in our projects, which are study, Concept and 0-date. (Please don't look at the names, they aren't that important.)

You can only go to the concept milestone if we have filled our study milestone and so on.

Right now I want to automate this process a little for input and reporting. Like the projects which are on milestone study and so on.

But I don't know how to start exactly on this one.
Has anyone had the same datamodel in the past ?

Thanks in advance,

Bjorn