If someone selections a s specific checkbox, is there a way to make a promo code required?

Hello,

Is there a way to require someone to fill out an additional field if they select a particular check box.

We have a list of check boxes that our customers can select from to select their desired sample. But, on a specific sample we require them to enter a promo code for that specific option.

This is the form that I am referring to: https://fs22.formsite.com/vistadental/form1/index.html 
This form is currently built and hosted on formsite.com.

I tried to clone the form, but it didn't work.
I have a rough draft going, but I cannot figure out how to get a required field to pop up if that specific sample is requested.

Thank you!

Please check my demo form: https://form.jotform.com/72915267528970

In my demo form, I used the Show or Hide conditional logic. If AAAA is selected in the Single Choice field then the AAAA field will show up. Same goes with the other selection. For more information about Show or Hide condition, please check this guide: How-to-Show-or-Hide-Fields-Base-on-User-s-Answer

For the Required fields conditional logic, please check this guide: How-to-Make-a-Field-Required-Based-on-User-s-Answer

If you need further help or a step by step guide on how I created the demo form, please let us know. Thank you.

Perfect! Thank you for your reply - it really helped out!