Block invoice from specific vendor when Invoice amount does not match PO price exactly

Hi,

Requirement:

Certain vendor has been overcharging. With the Tolerance Key PP set at lower and upper value at 25, the invoice gets blocked only if the tolerance was exceeded.
This is fine with most vendors in the company.

Except, this particular vendor needs to be blocked when the PO price does not exactly match the Invoice price.

I know this is not achievable through Vendor specific tolerance OMRX and OMR6 Configuration.

Is there any BADI/user exit to achieve this check for specific vendor or how do I attain this?

Regards,

SS