Dynamic header

I'm not looking to change the number of columns to be dynamic, as is the case with 90% of the posts that I've seen on the subject.

I have a report - 400 pages - of projects/tasks - in this report are vendors / invoices / expenditure types, etc.

About the first 250 pages are of expenditure class "Invoice", but then they switch to expenditure class "Miscellaneous".

If you are not on the page of the report where this switch happens, you do not even realize that the expenditure class has changed.

I would like to have one of the header columns to just say "Invoices" -- and then when the expenditure class changes, i'd like that to switch to "Miscellaneous".