Disable editing of some entries

We are allow users to apply to multiple projects using one form.  Users have a dashboard where users can see their submissions and edit them.  We would like to take away the ability to edit the submission once the project date has closed.

The application looks like (each project is a category):
What are you applying to:

o Project 1
o Project 2
o Project 3

So assume projects like:
Project 1 open
Project 2 closed
Project 3 open

User sees the projects he has applied to:
My applications:
Project 1
Project 2

Clicking on the project shows the details of that project with an edit link. How can I remove the edit option from the closed project (project 2.)

We have discussed using a hidden date field for each radio button that holds the closed date. Then using "if" in the view to show/hide the edit link. But, when Project 2 becomes available 6 months from now, users will be able to edit their old applications.

Also, it needs to be easy for the program administrator to open and close projects.

I am open to alternative ideas.

Thanks!