Header Configuration Beyond the Basics

I have a template drawing data from an XML with multiple invoices in it. I am able to repeat a header on every cover page of each invoice of the resulting output, but need these further things to happen:

1) If an invoice has data that runs onto a second page or more, the header doesn't repeat on those subsequent pages of that particular invoice (I have tried to enter in "Call Header" code before "Start Body" but that just makes a global header that is NOT unique to each invoice that repeats on every page; NOT what I'm after - I have conditional regions set within the header that make the output unique to each invoice so that they must not be a global header)