zero dollar invoices

Hi,

We are on 12.0.4, we have lot of iexpense (created by bothpay functionaly) invoices with zero doallar as invoice amount.  I want to have a payment template that should select only the invoices which have the amount of zero dollars so that I submit teh payment request and can mark those invoices as paid.

I have been trying all options but not yet successful, please let me know if you have any better idea.

Thanks,

Ravi