Hi Meruta,
You can achieve this by having a user status in Network and network activities. You have to create a user status in such a way that this will not allow TECO. When you TECO WBS, this user status will restrict you to change to TECO in NW and NWA.
You need to have another user status which will allow TECO so that NW and NWA can have TECO status whenever it is required.
Please let me know if you have any questions.
Thanks
Regards
Srinivasan Desingh