time entry update layout

Summary:

We have a custom layout for time entry. The custom layout has project/task as rows and dates as columns. We want to have users create rows and select project and task. But once the time card is saved we dont want them to change the project or task information. They have to enter 0 for hours and enter new row for the project.

Is it possible to have two layout options in time entry page. One to make project/task as read only, we use this after the timecard is saved. Another to allow to select the project or task. Is this possible to make it read only.