Price change allowed in entry sheet

The scenario - I need all PO that are created must have the indicator "Price change allowed in entry sheet" be checked when they are created by default. The settings in SPRO (Screen layout for external service management) allows that this field could be display, optional and required. But my requirement is that this field in PO must be checked and should be non editable (grey).

Also, what would be the best way to update all the POs that have already been created to have this indicator for every service items that are created.