Post vendor invoice MIRO only with parked document in MIR7

Hello,

We have implemented the functionality of Park and post in Vendor invoice. MIR7 would be used for parking vendor invoice and MIRO for posting parked document thr MIR7. We have given access also as per park and post to different different users.

Issue is that the User with MIRO access can also directly post the invoice by giving PO reference.

Pl suggest the way that the user with MIRO access can only post parked document (MIR7). The system should not allow to do MIRO if the user gives Purchase order as reference.

Regards,