Answer There's no way to force them to do this, but you could use a product-specific confirmation page related to the product they purchase to upgrade. On this page you can display instructions or include a form on what you'd like them update on their account.

http://support.membermouse.com/knowledgebase/articles/319138-create-product-specific-confirmation-page

This article on creating a form to collect custom data may also be helpful:

http://support.membermouse.com/knowledgebase/articles/319229-create-a-form-to-collect-custom-field-data