Filtering attachments on a delivery

Has anyone had any success with using the option "Enable filtering of recipients who will receive the attachment" in a delivery template?

I am trying to use one delivery template that should have an attached file for only some of the recipients receiving the delivery.

It looks like it is possible according to the documentation: https://experienceleague.adobe.com/docs/campaign-classic/using/sending-messages/sending-emails/attaching-files.html?lang=en

I am just not sure how to "define a recipient selection script", which is what according to the documentation is needed.