How to make attachments mandatory for last name change

Summary:

We have a requirement to make attachments mandatory when a user is updating last name

Content (please ensure you mask any confidential information):

Within the Personal Details page (Me > Personal Details) the business process for our client dictates that when making an update to your last name you must provide documentary evidence to support the change (e.g. marriage certificate). We have set up an approval rule so that the comments and attachments are visible when making an update to name but I am wondering how I would create a business rule that makes the attachments mandatory when updating last name so that users are not able to submit changes for approval without attaching the required documentation