When Customer Pays Invoice Online, Can We Require Custom Fields to Be Filled Out?

When Customer Pays Invoice Online, Can We Require Custom Fields to Be Filled Out?

Currently, our customers can view and pay their invoice online. If they chose to pay the invoice online, they are have to put in their credit card and their billing address. We would like to add 2 additional free text questions that would be required on the same screen. The customer would fill these out as they pay for the invoice online. Is this possible? This is the screen that we would like these two fields to appear on (and be required if possible):