Kanban with purchase order : avoid manual change status to full

Dear guru ,

i use a kanban with purchase order.

When I enter status empty (using for example PK13N) the system create purchase order.

I want to avoid that the users enter status full using PK13N or PKBC .

The users execute goods receipts against purchase order using MIGO in order that the system trigger status full automatically.

How can I avoid that users change manual status to full using PK13N or PKBC ?

Thanks.