how to insert a piece of text in all headers in a document with VBA

how to insert a piece of text in all headers in a document with VBA

all the answers I can find (and all the examples elsewhere on the web) are
about very complicated insert operations (only on 1 header, or only odd
pages, or not using select, or some such). How do you insert a simple
piece of text into all headers in a word document using VBA? Thanks.