KB Feedback Popup - Mandatory

Hello Friends, 

We are using HRSD Application and HR Portal and in HR portal - When users open KB Articles and bottom - options are coming to rate this article and Is this helpful or not and when we click on those options a feedback popup is coming, when users select not and give rating 3 or less than 3 then feedback popup details should be mandatory. 

 

Please  help us, how we can achieve this.

thanks, Basant