Block access to search help on a standard field

Hi

For my business activity I need to give an access to my prod SAP system to a customer.

This customer will create notifications with IW51.

The number of fields is very low, but a customer number is needed in the partner frame. As this is a standard field, access is provided to standard search help.

I don't want it. I would like to block access to search help. I tried to do it with a transaction variant, but I didn't manage.

Does anybody already faced such a need?

Any help would be very appreciated.

Regards

Olivier