add drop down list to a dynamic stamp

Hello: Is it possible to be able to create a dynamic stamp that will let you choose from a dropdown list and / or txt box prior to stamping it on the page.

What I am trying to achieve is create two types of stamps for our invoices

1) The dynamic "Approval" stamp is already good as it displays date and name but would like to add a drop down list that displays a list of GL codes

2) A voucher stamp this I simply want to have the ability to type in a voucher number. in addition to the date and person

Thanks all. look forward to responses.