Locking Product Schedules when Re-Calculating

When modifying Product Schedules on an Opportunity, you edit the Booked Amount fields.

Viewing the Manage Schedules page, you will see that the values in the Booked Amount column are always editable. However, you can add a lock schedule checkbox to the page via the fieldset. When set to true on a Product Schedule, this prevents the schedule from being recalculated in the auto-calculate function.