Further logic in email request for approval

I have an approval request workflow for approving incoming invoices. Since the person entering the invoices into an approval request form knows the person it needs to go to, they don't always know which project or cost category it should go to. I would like to see if there is a way to add further logic to the form that the approver sees in their email request for approval to 1. when they approve an invoice then 2. the form asks them to fill in a drop down of the project and cost category which will then get recorded in our invoice approval sheet.