ESR how to ask a question when the answer is just attachment an it should be mandaty?

Summary: This is for External Supplier Registration

Our requirement is to create a question: "Attach your W9". and suppliers should attach the w9 ONLY.

so I created a question with "Respond Attachment" Required but IT DOES NOT MAKE QUE RESPOND REQUIRED.

Supplier can submit the request without entering the attachment.

If I turn on the "Respond Required" Supplier needs to enter A) an answer in a Text box, and B) also need to attach the W9.

We want Supplier to enter the attachment ONLY. with not answer or comments for that question.

Is there any idea on how to do that?