The Lock calculation function is used to:
If a calculation has been locked, the calculation lines for the selected part cannot be changed. This means that no lines can be added or deleted either. The lock applies to all calculation lines: parts, operations, equipment, external operations, and surcharges.
The Calculation locked check box on the Calculation/production tab of the Parts form tells you whether the part calculation is locked.
Note: This function is only available if modification is enabled.