Make a field, provided by an app, required

[MeganEggLift]

I'm using the app "dcode - Discount in Cart".  There is a field in the Cart page for my customers to validate their Discount Code before continuing to the checkout.  

I want to make this field a REQUIRED Field -- Must provide valid Discount Code before continuing to chekcout.

Since it is an App, is this possible for me to impose the <input required class="required"    ?

Help appreciated