Dialog for Disqualifying a Lead

Hello everybody!

I'm looking for a way to have a dialog ask for a brief description field when disqualifying a Lead. I created the dialog with the prompt and the update record, but the question is how do I make this dialog run instead of the option set that pops-up when selecting the Disqualify option on the menu ribbon.

I'm using MS Dynamics CRM 2013 on premises. I appreciate any information.

Thanks

Carmen Wallis