I would like to make the answers to an assignment available only after a student has submitted the assignment.

I can see that I can lock an entire module until the student has submitted an assignment. But I cannot see any way to lock an individual item in a module, such as a content page which would contain the answers.

Each module contains readings, videos and assignments for 1 week.

I don't want to lock the entire weekly module, since some students like to do reading and watch videos ahead of schedule and then submit the assignments in the week when they are due. I want to offer students the students the flexibility to get ahead of schedule.