Restrict access to bid invitation cFolder documents

SRM Experts,

I have a requirement to restrict access to bid invitation cFolder documents.

Here is the scenario:

Buyer1 creates a bid invitation and a cFolder. We do not want any other buyers within our organization to access this bid invitation cFolder.

How can this be achived?

At this time, if a buyer (ex: Buyer2) has access to create a bid invitation or view a bid invitation, the system is automatically gives Buyer2 access to cFolder created by Buyer1.

This needs to be restricted, any advice would be appreciated.

Note: BADI BAdI BBP_CFOLDER_BADI is already deactivated in the system

Please let me know if you have any ideas.

Thanks