I want to be able to direct the user to a visualforce form before closing an Opportunity. Upon completing this form, I want the opp to complete its closing.
 
I'm relatively new to salesforce and salesforce development, but one alternative I considered is a validation rule that requires them to submit my form (and add a related custom object) before they are able to close the opp. This left me to add the form as part of a page layout or as a custom quick action. However, this is not ideal because I want the flow to be seamless for closing the opp. I want the form to be part of closing.

Is there a way to accomplish this?