cannot edit sales order that convert from negotiation with workflow (Negotiation Flow - Generic with

Hi,

i have face some difficulties for requirement from user.

for certain order type i will set for need negotiation and need approval (Negotiation Flow - Generic with Approval)  and the workflow is :

create Negotiation --> Approve --> Customer Acceptance --> Book Negotiation --> copy (for convert from negotiation to sales order) --> create sales order

After above step (i open negotiation and still can update the approved Negotiation, and also if i open sales order (created from approved negotiation) and i found out that i still can update.

my user complain because transaction that has Approved must be not capable to be edited !!